junk. i bought one, the plastic mounts broke and luckily i watched it fall off and went back and got it.
remounted it solid, and it goes off when ever you hit a bump, but not when you slow down. only works if you jerk to a stop.
took it apart, re-worked it, had it going for awhile, then it failed completely.
the chinese batteries aren't the same size as duracells from 7-11.
ended up throwing it away. uh... actually, i threw it into the wall outta frustration.
i emailed the company, and actually got a few responses, about their cheesy mounts, the bump fluctuation, and the overall shoddiness of their product, and they thanked me, and i never heard from them again.