Hi Russ,
I remember back in the early nineties making a 3 wire timer the 3 wires being hot ground and load. When you activated the timer by momentarily switching power to the load the timer would activate and hold power on the load for 15 seconds. The circuit used a transistor and a capacitor to feed the base and a 555 timer and another transistor to carry the load. My point is maybe you could use a capacitor on your inputs, when it charges up it drops the load and requires you to release the switch to reactivate.