Range Finder?

[Wzup4021]

I'm not sure if this is the right category, but I hope I can find some help. For this years competition we're looking at possibly using a range finder, however the one we have tried in the past (Not sure the exact model, it used radio waves is all that I know) didn't work out very well and wasn't consistent. Has anybody had luck with a good (Possibly infrared?) range finder that isn't very expensive? Looking for around a $100-$150 range. Any help would be greatly appreciated.

PS: Also, what makes a range finder legal/illegal for FIRST FRC?