Dalai

DC Rainmaker has a pretty good list of the available PM's.

Look and Metrigear (the later bought out by Garmin to become the Vector) were in a battle to bring their pedals out first. Look won that by a short margin, but had a number of issues and for those who want to use other head units weren't able to as Look / Polar didn't use Ant+ rather used Polar's data sending format.