They have those at our local sushi place in Oakland, Kansai. It's very relaxing not to have to deal with being bugged, but to know that you'll be able to get service when you want it. - Robin Barooah

I'd guess it's a reference. Our Kansai has giant TV screens showing either football games, or MTV, and is too noisy to tell whether the staff shout something when those buttons are pressed! - Robin Barooah