There are two different types, a dash mounted control (boo!) or the turn-signal 'piggy back' type (yay!).

You don't have to have any special existing equipment (i.e. variable speed sensor or other). It works off a 'transponder' (for lack of a better word) that you attach to your drive-shaft (to help maintain speeds up and down inclines) and a pick-up 9receiver) that you mount nearby.

My father-in-law installed one years ago and it seemed to work fine. A nice Saturday installation.

Good Luck,