We do Greenlight for this, which has a management app and a debit card. It’s not perfect, but it’s working well for our preteen son and is pretty flexible. We can add money when he completes chores and can partition what he can spend where. It works and he’s definitely gaining more of an understanding of how to manage his money.

Edit - Greenlight also gives you a qr code and payment link that (e.g.) his grandmother can use to pay him for mowing her yard, etc. No cash involved.

Thanks! About 5 hours into a new playthrough of BL2 with my wife, so this is awesome!