That's not a bad idea. You could use
some kind of USB dongle connected to a wearable? Once you walk away from computer it takes a picture of the screen( looks like nothing is changed), but the computer immediately locks down everything except what's currently on the screen.
Only a password along with the wearable would unlock it? (It's probally not easily feasible, but it doesn't sound impossible?) "Oh, I scratched my head, and my computer hard drive shut down."
