Good point, the choices are: smartphone, smart watch, physical bank card (credit or debit), and pre-paid "Oyster" card (think pre-paid debit card specific to t

Good point, the choices are: smartphone, smart watch, physical bank card (credit or debit), and pre-paid "Oyster" card (think pre-paid debit card specific to the London public transport network), and, yes, legacy paper mag-stripe tickets.