Sousveillance is the surveillance of a person on himself which can be done using cameras, audio recording devices, or GPS. Probably more ways than that too. 

Or, as Wikipedia says:

Sousveillance (/su??ve?l?ns/ soo-vay-l?ns) is the recording of an activity by a participant in the activity, typically by way of small wearable or portable personal technologies.

I think it's going to become a big thing in the near future. 

But first, one of the most obvious reasons I can think of for recording oneself is to protect from false allegations. Sousveillance can be used as an electronic alibi. 

Consider dash cams, those cameras that drivers can install inside their cars so that everything in front of the car can be recorded at all times. That way, if there's an accident, the driver will have video evidence of the crash, and that might be helpful in preventing the driver of being falsely considered the one who caused it. 

There are many action packed dash cam videos on YouTube if you want to get an idea what can be recorded in front of a car as it is driving.

But the use of sousveillance goes beyond just recording driving from a camera pointed out the windshield of a car. 

Wearable cameras worn by police would be another example of sousveillance. Though it's probably not each individual officer's choice to conduct surveillance on himself in this way. Perhaps it is in some cases.

Some people do - and I'm talking about regular civilian people - choose to strap a camera (or cameras) to themselves or use other means to record evidence of all of their activities. One noteworthy example of this is artist and professor, Hasan M. Elahi, who records nearly every aspect in his life in the form of pictures around him. He also records picture evidence of all of his financial transactions. And he logs his location using GPS.

Elahi seems to have started the activity of sousveillance, or surveillance on himself, after being mistaken by the FBI as a possible terrorist. 

This reminds me that there are many cases for sousveillance being used as an alibi. You can records your movements, your actions, and your speech so that you can provide evidence to help you in the event that a person may try to falsely accuse you of things.