I am looking for information regarding dual system pedals that come with some kayaks with rudders: the bottom part of the pedal is fixed and can be pushed against, while the top portion of the pedal operates the rudder. What is the name of such pedals? Where can they be purchased? Any information on the subject will be greatly appreciated.
Smart Track by Seal Line
There may be other manufacturers, but the one I have used is the SmartTrack system originated by Seal Line.
Here is a review from SeaKayaker: http://www.smart-tracker.com/seakayaker-B.htm
While not strictly meeting your description, there are also pivoting footbraces made by SeaDog that some people prefer over the SmartTrack ToePilots.
You can check them out here:
ONNO’s gas pedal system
About halfway down the page…