Ooh, this could actually be huge if it works the way I’m imagining…
If you’re a heavy credit card user so don’t use Monzo for budgeting, this would hopefully make that problem go away - create a group with your Monzo account and your credit card in and hey presto, budgeting/Left to Spend will work. And you should be able to see all the transactions from your credit card and Monzo account in one place. That could be a game changer!
(Side thought, I wonder if the open banking APIs would allow Monzo to pick up credit card transactions pretty instantaneously? Instant notifications / live updating from banks that don’t support it 
)
Just one plea - can we get away from calling it a Monzo Card? Unless there’s a bigger strategy at play here that I’m not seeing, the ‘card’ term is a hang over from pre-paid days - I’d much rather Monzo Account. And that’d let you decouple the card and the account ready for stuff in the future (for example, one card servicing both joint/personal/euro Monzo accounts - or if you wanted to play in Curve’s space).