The Prince Charles cinema puts up signs telling people to switch off mobile phones, not to smoke, and to refrain from talking during the film. This usually works, and all cinemas should do it.
(And perhaps they should also put up a sign telling people to keep their feet off the seats.)
I think mobile phone blocking devices would be too expensive. All the cinemas should need to do is put up a sign outside the auditorium telling people to switch of their mobile phones etc before going in, for the benefit of latecomers, and also put up a sign reminding people to switch off mobile phones before the film.
At my local theatre if someone's mobile phone goes off during the performance they have to pay a ten pound fine. And that's just an amatuer dramtics society.
