Be careful though, the Monzo current account conditions say that you are potentially liable for any losses if “you were very careless or you intentionally failed to keep your phone, card and PIN safe”
I’m not sure if this would count but if something fraudulent were to happen (with this and pretty much any bank), they might be within their rights to say you weren’t keeping your card safe by letting someone else have access to your account.
Just a worst-case scenario, not saying it will happen but its a risk.