Play Integrity API Checker is a free Android app developed by Nikolas Spiridakis. It falls under the category of Utilities & Tools and is a handy tool for checking the integrity of your device. The app is 100% open source, and you can find the source code on the developer's GitHub page.

The app shows information about your device's integrity, as reported by Google Play Services. In case any of the information fails, it could indicate that your device is rooted or tampered with, for instance, having an unlocked bootloader. However, it's essential to note that Google has a 10k requests/day limit, so if the app stops working, it's probably due to this limit.