I bought a house with these and didn't realize it had this feature for like a year (batteries had died). Now I love it. I find myself taping every faucet it use and am annoyed when others don't turn on.
I actually bought a handfree soap dispenser to go next to it, which is a great combo. Preparing meat or something, I can clean my hands and tap sink with elbow and not worry about cross contamination of everything.
Does anyone remember Moses meat shoes?