The best dashcam on the market is the Zetronix Blackbox unit -- without a doubt. I even have one in my black Prius and the heat is not an issue...
I also have it in my Roadtrek CS. It's great for:
+ Security - I leave it on when I am away from my coach. It even has a G-force sensor you can set to save any recording like if someone bumps your coach, etc...
+ Defense - It records front AND blind spots if I am in an incident and the other guy argues. You can tell the police to remind the other driver, "It's a felony to lie to me. The other guy has video. So, tell me what happened again..."
+ Refute - If you get a ticket in error there's no better evidence to take to court. I leave the sound on to record any possible interaction with the friendly police...
It loops the recording and you can just hit a button when something happens that you don't want erased. Best of all, it records the blind spots.
AND, it plots the whole thing on Google maps, showing your speed, location (both by latitude/longitude AND on an actual map!), your speed, direction, etc.
PLUS, I use its video out to send a signal to the TV in the back of the coach so guest can watch it all!
Hands down, it's the coolest unit, and at a fair price. Check it out even on Amazon and look at the reviews (and save 25%). Or, visit http://www.zetronix.com/720p-Wide-Angle-Dual-Car-Camera-with-GPS-&-Night-Vision-Dash-Cam(201)/product_info.html
I even put one in my Prius to protect me from the 'Barney Fifes' in the hick-county next door...