[pull_my_finger]

Seems like a call-light/attendant button (like in healthcare & airlines respectively) would be fairly inexpensive and make dining experiences wildly more efficient. Diners always outnumber servers, it would be nice to just press a button and let them know they're needed instead of having to crane your neck around looking for them and trying to get them to notice you so you can ask for your bill (or whatever else you might have needed).