A guy in our team does alot of modding, of his wheel etc etc, the sort of thing that costs £10 to do, but adds an additional16 buttons to the wheel (for messing with an old game pad and a soldering iron etc etc...)
At the moment hes looking into making a set of pedals which include a pressure sensitive brake pedal, know if that works, i'd happily hand over £150 to him
....assuming they work with a DFP - but i'm not really that technical, so i'm guessing they would be seperate with an individual USB etc etc...