There’s a DIY version, using IFTTT and a Google sheet. This is probably more complex as it works out a calculated daily budget to display as a widget, but the sheet could be modified to show the daily balance instead;
https://community.monzo.com/t/monzo-ifttt-share-your-creations-here/39383/153?u=davidwalton
(only for Personal Accounts, as IFTTT has no triggers available for Joint Accounts yet)