Bubble.io - Building tech is slow and expensive. Bubble is the most powerful no-code platform for creating digital products.
Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
Sheet 2 Site - Generate a website from 📗 Google Sheets
Xamarin.Android - Integrated environment for building not only native Android but iOS and Windows apps too.
Adalo - Build apps for every platform, without code ✨
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.