Mobile ads are intrusive and drain battery life. Current solutions often require root access or only work in browsers.
Build a non-root system-wide ad-blocker using VPN-based filtering or similar techniques. It should block ads in all apps without breaking functionality.
Monetize through a one-time purchase or subscription for advanced features like custom filter lists.
Start with a basic version that blocks common ad networks in popular apps.
The biggest risk is Google blocking the app from the Play Store, requiring alternative distribution.