Although I’m not sure Monzo will develop this (it’s quite hard to pack this functionality into a mobile app, for one thing), a few developers have already done it, using Monzo’s open API 
If you fancy checking it out (& you’re not afraid of a bit of tech complexity) then check out the apps here -
https://github.com/rdingwall/awesome-monzo/#apps
There’s some previews of some of those apps here 
