[[quoteright:280:[[{{Spider-Man}} http://static.tvtropes.org/pmwiki/pub/images/spideytracer_280_3641.jpg]]]]
A tracking device is a piece of AppliedPhlebotinum that broadcasts its location, and is used to follow the individual or vehicle it's been secretly planted on. Occasionally the individual discovers the device and uses it to lead the trackers on a WildGooseChase.

Tracking devices can also be intentionally used by characters on the same side to keep tabs on each other, so that if somebody gets kidnapped, his friends will immediately know where he is. Of course, a GenreSavvy bad guy who happens to ''find'' a tracking device used for this purpose could easily use it as a RedHerring.

Most tracking or surveillance devices depicted in fiction are so small that they cannot include important components such as a power source, antenna, microphones, etc. This used to seem like magical tech back in the day, but as TechnologyMarchesOn with the advent of mobile phones that allow tracking by cell tower, and USB Pen Drive-sized GPS trackers, extremely miniature tracking devices are rapidly becoming TruthInTelevision. Indeed, any tracking device that isn't miniscule these days probably qualifies as an IncrediblyObviousBug.

Compare the SubTrope TrackingChip, when a tracking device is implanted.
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!!Examples:

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[[folder:Anime & Manga]]
* Early in ''Manga/MagicalGirlLyricalNanohaViVid'', after [[spoiler:Hegemon Ingvalt]] walked away in apparent victory, the near-immobile [[spoiler:Nove Nakajima]] contacts [[spoiler:Subaru Nakajima]] and [[TheReveal reveals]] that she planted a sensor on her during their battle, so they can track her down and capture her at any time they want.
* More like the fun tracking programs you can get for your cellphones to track your friends, Pockets in ''TowerOfGod'' have this option that two mutually registered Regulars can track each other.
* Both the heroes and villains use these in ''Anime/ScienceNinjaTeamGatchaman''. Finding or evading them are plot points in several episodes.
* ''LightNovel/AiNoKusabi'' has "[[SexSlave Pet]] Rings" which all have built-in tracers to track a pet's whereabouts. One pet in particular finds this out the hard way.
* ''GhostInTheShell'' has tracking devices which can be fired out of pistols. In both the movie and the show, Togusa fires one out of his revolver to track a car.
* In [[Manga/CountCain the Cain Saga]], [[spoiler: Cain's earring]] works like this in a steampunky kind of way, being made of a special stone that causes a larger piece of it to resonate whenever in proximity.
* Hanaoka the butler from ''Manga/SangatsuNoLion'' lets slip that he keeps track of Nikaidou through GPS before poorly covering up with an alternate explanation as to how he's able to find his young master so easily. Played entirely for laughs.
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[[folder:Comic Books]]
* Often used by Franchise/{{Batman}}.
* Also commonly used by {{Spider-Man}}.
** It was a {{Spider-Man}} comic that led to the invention of electronic tagging.
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[[folder:Film]]
* The ''Millennium Falcon'' gets one in ''Franchise/StarWars'', leading the Death Star to the rebel base at Yavin.
** Jango Fett's ship also gets one on it in Episode II.
* Used to hilarious effect in ''Film/TheNakedGun'', where Nordberg fails to attach the tracking device, rolls down a hill, and ends up underneath Drebin's own car- "we're right on top of him now!"
* ''Film/TheAvengers1998''. Steed gives Mrs. Peel a set of boots with an implanted "micro-tag" (radio homing signal). He later uses it to locate and rescue her.
* Johnny Five from ''Film/ShortCircuit'' has a tracking device that he tosses into the bed of a passing pickup truck.
* In ''Film/TheMatrix'', the three Agents implant a literal (robotic) bug in Neo's body that they plan to use to track him.
* ''Film/RedDawn1984''. The Soviets capture one of the American guerillas and force him to swallow the tracking device. Unfortunately the ''spetsnaz'' team they have following him gets ambushed, and their homing beacon points directly at the traitor.
* ''Brannigan'' (1975). The police plant a magnetically-attached bug on the vehicle of the mob lawyer used to make the ransom exchange, but he finds it and plants it on another vehicle while stopped in traffic. Unfortunately JohnWayne has planted a second bug inside one of the bundles of ransom money.
* ''Film/JamesBond''
** Bond plants one in Auric Goldfinger's Rolls-Royce in ''Film/{{Goldfinger}}''. Felix Leiter later homes in on the smaller one Bond is carrying to locate the OO agent.
** ''Film/TheManWithTheGoldenGun''. Mary Goodnight wears a homing device as a button on her clothing. {{MI6}} uses it to locate her after Scaramanga kidnaps her.
** ''Film/NeverSayNeverAgain''. Fatima Blush plants one on Bond so her electronically controlled sharks can home in on him.
* ''Film/TheAdventuresOfBuckarooBanzaiAcrossThe8thDimension''. There was apparently one of these on the Oscillation Overthruster (or possibly Penny Priddy), as Buckaroo uses a signal detector to find them inside Yoyodyne.
* ''{{Film/Aliens}}''. Corporal Hicks gives Ripley a wrist mounted tracking device. Ripley later gives it to Newt. Near the end Ripley uses the signal to find where Newt is[[spoiler:only to find it lying on the floor after being torn off accidentally or deliberately by the xenomorphs. Ripley breaks down in tears, but fortunately Newt is still close enough that Ripley hears her when she screams.]]
* ''Film/MissionImpossibleGhostProtocol'' has the target being given papers impregnated with a unique radiation signature (in case he's smart enough to throw away everything else, they can still track him). The only problem is that Ethan Hunt needs to keep the target in visual range, which is nicely ironic when he ends up chasing the target through a zero-visibility dust storm in Dubai. Ethan uses the tracking device to manoeuvre his car into the path of the oncoming vehicle, leaping out moments before [[CarFu the cars crash into each other]].
* ''Film/EscapeFromNewYork'' has two of them.
** Snake is given a tracer. When he pushes a button his position can be tracked for 15 minutes.
** The President is wearing a vital signs bracelet that broadcasts a "sig pulse". Snake is given a device that can home in on the signal, showing direction and distance to the device.
* In ''Film/TheAndromedaStrain'', (1971) the four scientists (Hall, Dutton, Leavitt and Stone) can be tracked by the first letter of their last name on the electronic diagram, anywhere in the Wildfire complex.
* By way of a translucent red stud on the back of Emmet's leg, Film/TheLegoMovie utilizes this trope. Early on in the film, Emmet gets shot in the back of the leg. He himself doesn't see exactly ''what'' he was shot with until somebody asks "What's on his ankle?" Cue OhCrap moment.
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[[folder:Literature]]
* Frank Herbert's ''[[{{Dune}} Children of Dune]]''. When Alia sends Buer Agarves on a diplomatic mission to Stilgar, she conceals a homing signal in the new boots she gives him so her forces can follow him and capture Stilgar.
* In the Literature/VorkosiganSaga novel ''Komarr'', Miles briefly thinks he'll be able to get a lead on the villains when they steal his Auditor's seal, which has a tracking device embedded in it. Unfortunately, they know about the device, and almost immediately flush the seal down the toilet to serve as a particularly messy RedHerring.
* In Creator/RobertAHeinlein's ''Literature/TimeEnoughForLove'', Lazarus Long {{Time Travel}}s to meet his family when he was a child. Due to a miscalculation, he winds up in 1917 instead of 1920, just in time for the United States to get into WorldWarOne. Prior to leaving, he was unknowingly implanted with a tracking device by his family of the future, which comes in really handy when he gets shot in battle and has to be rescued.
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[[folder:Live Action TV]]
* May be one of the most used devices in the series ''Series/{{Alias}}''.
* The title character of ''{{Chuck}}'' wears one in his wristwatch so (theoretically) his handlers can always find him.
* In the ''Series/{{Leverage}}'' episode "The Stork Job", Hardison reveals when Parker goes off on her own that he put a GPS tracker in her shoes. It's implied that he keeps tabs on the entire team this way all the time. He also often uses the various [[EarpieceConversation magical earpieces]] that they have for this purpose as well. Fitting this trope those devices are sufficiently small that there is no way that they could ever really work.
* Often used on ''Series/{{NCIS}}'', for the agents themselves to be rescued or just followed, or suspects or criminals.
* Used on an episode of ''Series/{{Scrubs}}'' so JD can track and avoid the [[AlmightyJanitor Janitor]].
* In addition to their primary purpose as CommLinks, communicators in ''Franchise/StarTrek'' are used as locating devices. Plots frequently demand that they be removed or jammed.
* Used over and over again in ''VeronicaMars'' in order to track and find nearly anybody.
* As part of his release agreement with the FBI, Neal Caffrey of ''WhiteCollar'' has to wear an ankle tracking bracelet at all times (until his 4-year term is up, anyway). He cannot leave a 2-mile radius of his home (which, fortunately for him, is in Manhattan) except with an [[FBIAgent FBI escort]], and if he tries to remove it without authorization (occasionally given as part of an operation), it sends out a signal.
* Used in ''TheCityHunter'': Young-ju bugs the [[VigilanteMan City Hunter]] during their first fight. Yun Sung later bugs the [[spoiler: stolen 2 million dollars]] in [[CorruptCorporateExecutive Kim Jong-shik's]] house.
* ''Series/BuffyTheVampireSlayer'':
** The Initiative shoot Spike with a tracking device which GenreSavvy Xander recognises because it [[IncrediblyObviousBug blinks for no apparent reason]]. Well, maybe that comes in handy when tracking vampires in the dark.
** Willow's oft-used "locator spells."
* ''Series/{{JAG}}'': Used by Clayton Webb in his first dealing with Harm and Mac to track their car in "We The People". However, they're GenreSavvy enough to leave it.
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[[folder:Tabletop Games]]
* ''{{TabletopGame/Shadowrun}}'' had the AOD (Activate On Demand) tracking signal. It only transmitted when it received a specific coded signal, which meant it could not be detected by standard radio detection techniques except when it was actually transmitting.
* ''TabletopGame/VictorianaRPG'' supplement ''Faulkner's Millinery and Miscellanea''. One possible Complication (drawback) for a magical clockwork limb was a tracer device implanted in it, which allowed someone to know where you were at all times.
* Iron Crown Enterprises ''TabletopGame/{{Cyberspace}}'' main rules.
** The Homing Device was a constantly broadcasting high frequency transmitter implanted in a living creature (such as a human being). It can only broadcast a few kilometers away.
** The Arm Sentry is a small device strapped to the arm of guests in corporate areas. It constantly broadcasts its position to the company security computer. If the wearer enters an area they're not authorized to be in, the computer sounds an alarm.
** The Tracer is a transmitting device that is either worn or implanted. They can be traced over great distances by ground-based or satellites. All Corporate and Government personnel have these implanted in their bodies so they can be recovered in case they're kidnapped or become lost.
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[[folder:Video Games]]
* Franziska plants one of these on her incompetent detective partner Gumshoe in ''AceAttorney Justice for All'', much to Gumshoe's displeasure.
* In ''VideoGame/MassEffect2'', after you acquire [[spoiler:the Reaper IFF chip]], it installs a virus into the Normandy's computer that broadcasts its current location. Which results in the kidnapping of all of your crew except Joker. [[spoiler:Kinda makes the Paragon choice in the endgame (to destroy the Collector Base rather than reverse-engineer it) seem the right one: if a mere chip made by the Reapers could outsmart the best AI humans could produce, what would an entire base do?]]
** ''VideoGame/MassEffect3'' has Miranda [[spoiler: plant a tracer on Kai Leng on Sanctuary, leading Shepard directly to Cerberus's main base]]. The spoiler for ''2'' is also revealed to be [[spoiler: fairly irrelevant. Even if blown up, enough of the base remains that Cerberus undertakes major salvage operations and some degree of indoctrination and so on happens anyway]].
* ''VideoGame/GhostTrick'';: [[spoiler:Cabanela fires a special bullet into Yomiel's body, which can be tracked by a modified pocket watch.]]
* In ''SecretAgentBarbie'', {{Franchise/Barbie}} has a gadget which is basically tracking ''perfume''.
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[[folder:Web Comics]]
* [[http://www.irregularwebcomic.net/comic.php?current=1460 This]] strip of ''IrregularWebcomic''.
* In RankAmateur, GELF are officially required to wear these. They were generally fitted to GELF even ''before'' it became law.
* In addition to working as a MindControlDevice, the iKnow from ''Webcomic/CommanderKitty'' can serve as one of these.
--> Zenith: What does that ''beeping'' mean? Is he getting ''close?''
--> Fortiscue: Oh...[[http://www.commanderkitty.com/2010/12/12/nothing-to-see-here/ shucks]].
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[[folder:Western Animation]]
* Played for laughs in an episode of ''WesternAnimation/JackieChanAdventures''. An episode that involves clones of the heroes has Captain Black place a tracking device on one of the Jackies. He starts bragging about it before the real Jackie points out that it's on him instead of the escaped clone.
* Also played for laughs in ''WesternAnimation/InvaderZim'', where the "tracking device" turns out to be GIR clinging to the back of Dib's [[RunningGag enormous head]].
* 1973-74 ''WesternAnimation/SuperFriends'' episode "The Planet Splitter". The Super Friends put microdot homing devices on the remaining 100+ carat diamonds so they can be tracked down after they're stolen. At the end of the episode, Wendy puts Wonder Dog on a diet, them puts a microdot homing device on one of his favorite steak bones so they can track it when he steals it.
* Also in ''WesternAnimation/SwatKats''. Hard Drive and Dark Kat stole the Turbo Kat and used it to commit crimes and frame the heroes. They demanded several bags of money. Commander Feral hid a tracking device in one of them. The bad guys throw away a bag (presumably the one with the tracking device) and, using a device to impersonate T-Bone's voice, said "Nice try, Feral!"
* ''WesternAnimation/KimPossible'' sometimes uses various kinds of trackers, including tracking powder [[spoiler:(got in the vent system of the building)]].
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[[folder:Real Life]]
* Modern cellular phones have GPS receivers in them to provide locations during emergency calls. Some offer tracking services that allow account holders to keep track of their children, or track a lost or stolen phone.
** Sadly, these capabilities are also increasingly used for [[StalkingIsLove more]] [[StalkerWithACrush nefarious]] [[DomesticAbuse purposes.]]
* [[http://www.scotusblog.com/2012/01/opinion-recap-tight-limit-on-police-gps-use/ US vs. Jones]] resulted in a decision that, within the USA, use of such a device without a warrant may violate 4th amendment rights.
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