I do love the idea of the surprise and delight technique- and the first few times I got the Raiz notifications I was super impressed, my feelings changed after a while though because it became almost commentary on my behaviour, and to your point, not helping me improve my spending behaviour in anyway. Your example of how much you could earn in interest on that money would be awesome - but the click through function would be what makes it so much more likely for me to actually save or invest that money, rather than just think “cool I’ve got $300 to hit up Myer with”.
Edit: just saw your other question … I don’t think a banking app restricting my withdrawals would work for me… I like the idea of something like the CommBank spend tracker for example, something that shows how I’m tracking but doesn’t stop me spending more if I need to.
I use PictureWealth and Raiz, the tracking functions in Raiz I haven’t played around with too much, but I like the notifications. Picture Wealth has a really good budgeting/spend tracking function that works for me, but no notifications on how I’m tracking - so it’s up to me to be proactive.