This seems solvable. Most of the phones are used with SIM cards and have non zero balance. For instance we might make a law that the last $5 from cell phone su

This seems solvable. Most of the phones are used with SIM cards and have non zero balance. For instance we might make a law that the last $5 from cell phone subscription plan can be spent only on emergency calls, nothing else. This will make sure that any phone in active use will have enough balance to make couple of emergency calls. Proving identity can be as easy as scanning your fingerprint twice to unlock the phone and then confirm identity proving operation in crypto wallet. And we can still process calls to 911 without identity or payment but only if we have enough capacity to do so.