Hey I tried it and got it going really well, i changed some values to make it more sensitive (I don't have much space available for the pad) ie - changed the resistor to 100K and put a 1ms delay in on the charge, through a 3mm sheet of glass a sensor pad size of down to 6mm x 6mm worked reliably. This was using a 16F676 @ 4MHz. Why is rsocor using a 16F84? I cant even understand why they are still being made and so popular, they are just junk along side the more modern chips.

Thanks Mister E for such a great idea, I think as long as I tune the sensor pad size/resistor it should be pretty reliable as I've had no issues with it yet and it worked first time.