Thanks very much for the info and links.
I think this might be above my pay grade as a former software guy. I was hoping to simply stick a battery operated button onto the tethered cable of my home charger that replicates the open charge port functionality of the Tesla plug. When getting out of the car, I often forget to open the charge port. I find tapping the door to be hit and miss, it only works if the car is unlocked and it sometimes manages to lock itself by the time I get round the back.
I know next to nothing about AC electrics, so I would be very wary of taking apart my charger and modifying it.