I have the "4Sight" dashcam in my car and TV. Not cheap, but has every bell and whistle you can think of. Audio, front AND rear simultaneous video, GPS, speed, KML Google map tracking, 32GB card, loop recording, impact recording, both front and rear cameras are adjustable, etc. I've had both units since 2012 and no problems. Video is crystal clear to the point you can read the tags of cars near you and identify faces of drivers.
Cost about half of most high-end dashcams. I think I paid $220 for mine AND it does front and rear at the same time.
2013 Silverado 2500 HD Duramax/Allison Tuned
Aviator Wright Flyer #1919
"First In, Last Out". 11B4Y
DAV, MOPH, VFW, 5/7 Cav,1/8 Cav Assoc.
11th ABN Pathfinder Co. N7MIP