I think Steve had a great idea. That should be included in the restaurant reviews. With that said there are lots of places like Las Vegas many parts of Mexico that have "Valets" inside the restrooms that hand you towels etc. expecting tips. Geez, in Paris I went into nice places that did not have toilets, just a place to place your feet. :(
Bye the way does the person guardding the toilet get a cut of the cash?