Haha. The way I do it with smartphone is to “trick” myself into saving more/spending less:
I allocate money to my Starling account which I have budgeted for general use (fun/discretionary spending) and set up auto round ups on all transactions (x2). This means it looks to me like I’m burning through cash quicker than I am so I start easing off spending sooner than I would otherwise - “Do I really need XYZ? I’ve only got £XX left this week!”. Then at the end of the week/month or when I remember I look at my pot > "woo! extra money!" (a bit like finding a tenner forgotten in a pocket).
I either then save this as extra - or just ‘roll it over’ into the next fun budget so I need to ‘top up’ my spending card less. I find overall this helps me spend a bit less/more thoughtfully without actually feeling like I am constraining myself or having to set strict budgets for everything.