Raiden: So Dok, what kind of data can you extract from those left hands, anyway?
Doktor: Oh, all manner of information. But, the short list? Energy consumption, damage level, intracranial and blood pressure, blood sugar, other vitals... GPS history, speed and acceleration data, radio and optical readings... Recorded computations from the internal expert battle-support system...
Raiden: Uh, Dok?
(A bit later in the conversation...)
Raiden: Makes sense. But why the left hand? Why store it all there?
Doktor: Accessibility. A unit can remove it with its own right hand, or it can be recovered if the unit is damaged. I would advise you not to remove your own holographic data storage, however, unless absolutely necessary. To facilitate recording of everything you see, hear, and so on, it is tied directly to your cranial nerves. So each time the storage is connected or disconnected, your hippocampus is stimulated. This can result in memory loss, flashbacks — (and) all manners of...unpleasant effects.