The TruScene is a device that will actively monitor and record around your vehicle. It does the recording in 30 second clips and will only save the clips if a sudden bump or jolt occurs—perhaps from a hit and run.
The TruScene could be really helpful making those hit-and-runners burn in hell—well, a hit and run isn't punishable by death, but it should be. This device has an estimated price of roughly $1,000 each. So if you want to monitor both the front and rear, it will cost a lot. The TruScene should be available later this year.