Here's what I run:
My dashcam. It's very simply to hook up, dead reliable, and has tons (and I mean TONS) of attachments to use it in every situation. Additionally, it has the exact same form factor as a GoPro (and very similar image quality) so all of the attachments are interchangeable. The LCD screen on the back is very handy to preview accidents at the scene.
Here's a full walkthrough of the camera:
<iframe width="560" height="315" src="https://www.youtube.com/embed/xnHDu-oW7_Y" frameborder="0" allowfullscreen></iframe>
Now, you could use a cigarette lighter to power it, and that'll work perfectly fine. Or, you could do what I do, and hardwire the cigarette lighter to an available fuse spot under the dash. Then, simply hide the wire inside the headliner and run it up to the camera. Both are perfectly acceptable.
Here's some footage I've captured with mine over the years:
Wrong way driver:
<iframe width="560" height="315" src="https://www.youtube.com/embed/TZsbOlmNOaU" frameborder="0" allowfullscreen></iframe>
My wheel falling off on freeway: (skip to 2:25)
<iframe width="560" height="315" src="https://www.youtube.com/embed/k18YreHlooQ" frameborder="0" allowfullscreen></iframe>
[MENTION=116387]Unner[/MENTION]