In London you can use a normal contactless debit or credit card or NFC payment on a phone for public transport. This is great for Londoners, and even better for visitors who don't need to figure out what they need to buy or how to top up a card.
I don't belive the ticket apps being discussed keep a balance, but I haven't used them myself.
I don't belive the ticket apps being discussed keep a balance, but I haven't used them myself.