Im running KCI communications black box.
Smart Black Box | High Resolution Mobile Event Data Recorder
All in one Camera, GPS, 3-Axis Shock sensor.
It automatically deletes older data when you run out of memory card space.
I guess you could wire it to always on, but I only have my on when the car is on.
Heres what the unit looks like mounted.
Passenger's View:
Driver's View:
Outside:
Videos are sync'ed with google maps so when you review them, you'll see exactly where you've been.