Hi,
my first post in this thread, but i did start a related thread a while ago 'Automatic vibrator to control orgasm' or something like that title, I expect you have seen it.
It's good that someone else is actively building and trying out stuff like this.

I haven't done any hw or sw aimed at ...

An idea used in the 'Terri and Jennifer' self bondage saga was to have the spare release key in a bucket part filled with engine oil, which you can pull down off the wardrobe in emergency. Penalty for use is a serious mess.

This has long been a fantasy of mine, and I'm considering developing one.

You've probably seen or experienced an ECG at some time. A bunch of wires and sticky pads are put on your skin, and then a sensitive machine records the electrical activity from the skin and deduces what your heart's doing ...