I use and am very happy with the Blackvue DR600GW-HD, but I'm pretty sure I pad more than $100. There are people upgrading all the time and you might be able to find one on eBay, etc. lightly used.
The Blackvue is essentially invisible unless someone specifically looks pretty hard for it. I didn't want to give anyone an excuse to break in and steal anything. Additionally I end up going thru a DWI checkpoint about every other week and although I've never had any problems I've seen some abuse. I'd prefer they not know I'm recording everything (both audio and video). The video is excellent HD both night and day. I have a couple of accidents caught on video that are pretty dramatic.
I know you have a budget, but sometimes paying more is worth it. A few weeks ago I had to make an emergency stop when a driver completely ignored a red light. It was close, and had there been an accident it would have been my word against the other driver regarding the light (not many witnesses want to get involved).