Rapid Fire Any Button!

[xSLICKVICx]

Hi I recently was searching on ebay for a new controller and found this http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270309143332&ssPageName=ADME:X:RTQ:US:1123
He says that there is a turbo button where you press then select any button you wish to have rapidfire and there you go, you will now have rapidfire on the button you pressed.

Does anybody know how to make this cool rapidfire mod or is there a kit available? Also if there is a kit, is it possible instead of making a turbo button, use the sync button?