Just came across this while browsing electro-music.com:
http://matrixsynth.blogspot.com/2007/07/mempot-potentiometer-with-memory.html
Imagine what a cool lfo or envelope this could be! Record the motion and fire it with a trigger!
I already made a topic at the bottom of same category. Lets not repeat ourself. OK? 
ok. hadn´t noticed.
Always a good idea to search before posting 
There’s a lot around!