They've already said you won't need a mobile phone. They mention phones as a deliberate distraction from the fact that they will be building a huge central database.
I will be very surprised if the app does much more than dish up a pre-signed chunk of ID data, much like an e-passport does now. It won't actually need a secure device.
(Which isn't to say they will support anything except android and iphone.)
They have said it will work for people who "aren’t able to use a smartphone". Nothing is said about people who are able but unwilling. I can only assume I will forced to submit to the terms and conditions of a foreign corporation, and forced to use non-Free software.
