Earlier quoted context omitted.
There's nothing that requires a microcontroller to be active during power-down to handle the issues you describe: For transit passes and IDs, there need to be non-phone-based ways of handling that issue. It's equally possible to lose / have your phone stolen. Talk to the station agent, or have the police look up your license by name / address. There's no need for a continuously-running microcontroller to read the pow…
> For transit passes It’s interesting, here in the U.K. you have a legal obligation to present a valid ticket upon demand for any train you travel on. Failure to do so for any reason (including my phone died, or I dropped the ticket) is a criminal offence (and I mean criminal , not civil) punishable by a prison sentence. Some ticket conductors at the end of a long shift hearing endless excuses about why someone doesn…
a) spend 15 minutes writing up a ticket, and possibly waiting for the police to arrive before handing you over to them
b) take you to the back office and let you sit for 5 minutes while your phone charges
Nobody is going to send you to prison for the first offence of not having a ticket (a physical ticket could be lost or damaged to a point where it is unreadable too). They would probably issue a fine, but you could appeal that. Buying a digital ticket you'd have a digital paper trail showing you bought it - which you wouldn't if you bought a paper ticket.