Go to amazon and look at the reviews on most of the dash cameras from $50- $200 , most are junk and just don't work properly or you can't view or download the videos when you need them.
Mine will be used for accident proof and tickets, it sucks but you really need one in your car to protect your legal rights today.
I bought a $100 from pep boys and returned it the next day, didn't work and I also went and tried the go pro hero 3 , but it costs to much and its not that practical and I returned it.
Best deal on the market is the JVC action cam, it will operate in 740 dpi in loop mode and can be charged by a cigarette lighter usb charger in this mode, all you need extra is a good mount and the memory card. Also it comes with a built in lcd screen that other cameras charge extra for.
Note make sure what ever action cam you get that it has loop mode.
Best buy only $199
JVC ADIXXION HD Flash Memory Camcorder Black GCXA2BUS - Best Buy