Take two bound guys and see who can be forced to cum first...
Two cocks rubbing against each other in a flesh light
Two cock tied to a vibrator
Stop / Go... two or more guys stoking each other or using a vibrator. Signal is to cum while still being stoked...but for how long? Now signal is to stop while still being stroked...but for how long? The bound contestants want to cum but only when the signal is Go.