Cameras and recording devices have been prohibited at the majority of live performances since recording devices became practical to carry. Why on Earth should a recording device suddenly be exempt because it is buried in a phone?
I went to see a play in a 300 seat venue on Friday. and was blessed with being adjacent to a drama school group. The on-again off-again blue glow from these infernal devices was bloody distracting. I must, however, concede that I saw nobody recording the performance or using a flash; just completely ignoring the show. I realise that teens and 20-somethings cannot imagine a life without their personal phone but I also wonder why the phone is more important than the music/play/ballet/opera/whatever that they paid good money to see.