Ha! Certainly tit clamps would add entertainment value. Thinking along the lines of "leaving him to it" to work to release himself I wondered about swapping the dildo for an electro one, or if that wasn't practical then some electro pads on the balls. The control box could be set to turn on low but ramp up every few minutes automatically so the slower the boy went the more he risked fried balls. Should be possible to set it so that the final few minutes - when he's at his most tired - would be a frantic race to avoid the full on electro blast before the key was reached. 