Interesting. A google search for homemade pinball turns up a few, but they seem to have built some custom hardward to get it to work, and are at least a few years old.
I was thinking an add-on to VP, which would work like this:
Add a mapping feature for all switches that can be hit. This would be targets, dropdowns, slingshots, rolloevers, etc. Bring up a mapping feature, which will list all these elements in a grid (so left slingshot can be assigned to any key, for example). Similar to the Ultimarc IPAC configuration.
Then wire the left slingshot switch to that key on an encoder. When you play the game, the ball hits the left slingshot, and passes that key back to the PC, which awards points (and drives the slingshot solenoid, somehow).
It would probably be easy to do outside of VP, but if it could be added on, any existing scripts for games could be used. Just recreate your virtual playfields and play the real thing.
Anyway, I'll stop hijacking this thread. Maybe I'll start a new one about this...