It seems that the Real Life section would need a thorough cleaning: a lot of the examples simply don't qualify. The Spartan krypteia was a Secret Police, but the Spanish Inquisition, CIA, KGB, etc, never were, even if their activities were free from official regulation or inquiry. According to the trope description, it's only *secret* police if it doesn't *exist* officially.
The description of "Verfassungsschutz" is somewhat misleading (they're a kind of secret service thing; the closest equivalent I can think of would be the FBI), and somewhat gushy. Also, with recent political events (early/middle 2012), they are coming under increasingly close scrutiny. On the other hand, they don't really compare to the other examples either. Can I pull it or at least rewrite the description completely?
Note regarding the Sheriff's Secret Police from Welcome To Night Vale which I haven't researched adequately for inclusion in the page. "Secret" could in fact mean "identities unknown when not in uniform" rather than "you don't see us at all"; the only spokespeople with names aren't part of the organization and they show a strong preference for anonymous communications. While it's not really normal for that kind of "secret police" to be in uniform doing regular police-like work, it seems a plausible explanation for the name.