The publishing sensation run fat boy run, or similar gave me this idea. A little electric unit clips onto the waistband of your running shorts and if you are not jiggling it about as you would when you run, the unit pumps a nice wallop of voltage up yer kayser.
Wayhay off you go again. No way to switch it off until you reach the end point and deactivate it.
StunPants 2000 might be the market entrant.