What could go wrong with keeping mission-critical keys on a device that's capable of transmitting data without the need for a physical connection 
Apart from that I don't hear very good things about those operating systems on the phones, so it may still be of some use to people using it as a wallet.
Couldn't you use a micro usb adapter and a fresh android phone, load the package for file explorer and cold wallet generator apk's? Install them and never use data? Apart from that I don't hear very good things about those operating systems on the phones, so it may still be of some use to people using it as a wallet.
