Hmm, so what you need is a credit card with an extremely short billing cycle (i.e. settled daily using your debit card) and limited to a single "class" of expenses (car rental). I've spend some time thinking how a kind of Twilio for credit cards would work - an API to generate an instant card number with the exact terms you need. The main use case I considered was a card for online shopping that would only be good for use with one single merchant - then I can shop without worrying what will happen if they haven't secured their database correctly.
> The main use case I considered was a card for online shopping that would only be good for use with one single merchant - then I can shop without worrying what will happen if they haven't secured their database correctly.
I've seen this in a few places, but it seems to only be limited by expiry. Yes, it's a little easier to deal with if the number is compromised and you have to cancel it, but it doesn't actually offer any added protection - I think?
