they blink your number if its over about 3 or 4 the S.L.

EDIT: realized i hadnt contributed for reason thread was started. i vote for the sticker on the passenger visor

I've noticed it often giving the speed of someone else around me also.
There's one not too far from where I live and I either get "SLOW DOWN" or a speed that's vastly different from my own and ends up being the person in front of, or behind me. Heh.