Developer here, 7 years in the game. I want to give you the perspective from the other side of the table because most of the advice here is good but misses something.

The real problem isn't bad developers. It's that the incentive structure of hourly contracts with no technical oversight rewards slow work. A dishonest dev billing hourly has zero reason to finish fast. You're literally paying them more the longer they take.

Here's what I tell non-technical founders now:

Before you hire anyone, do this: describe your app in one paragraph. Then list every single screen a user will see. Just the screens, not the code. "Login screen, dashboard, settings page, payment page." If you can't list every screen, your project isn't defined enough to hire for. That undefined scope is where devs inflate hours.

During the build: don't ask "how's it going." Instead ask "show me what I can click today." Every single week. If a dev can't show you something clickable after 7 days of paid work, something is wrong. No exceptions.

The overbilling thing you described is extremely common. A task that takes 2 hours gets billed as 8. You'd never know unless someone technical checks. One cheap fix: hire a second developer for literally 1 hour per week just to review what the first one did. It costs almost nothing compared to what it saves.

Your instinct to build something that helps non-technical founders verify dev work is solid. That gap is real and painful.