With the introduction of joint accounts, I’d love to see Monzo use the opportunity to gamify saving or good budgeting between the holders of the joint account.
For example, if I could score a point each day that I spend less than my husband and vice versa, I think it would be an interesting way to save money.
Extending the idea, you could set individual category budgets, for example my husband commutes to work so it wouldn’t be fair to penalise him as he will always spend more in the transport category, but it would be a fun little add on to get competitive over who spends the least on lunch or coffee.