«version-controlled using git» for what? how useful would this be?
It's useful for tracking history, reverting mistakes, and making backups (git push).
what do you do with it, could you give us an example?
Personal finance. Track income, expenses, and bank account balances across multiple banks in multiple currencies. The information is useful for budgeting, and for monthly bank statement reconciliation (which allows the detection of suspicious/incorrect transfers of money).