From Reikan Technology Ltd:
FoCal Mobile provides a user-friendly auto focus check and calibration tool, taking the most useful parts of FoCal Pro and making them available for use on iPhone, iPad and Android devices.
Focus calibration and AF system check work with all cameras supported by Reikan FoCal Pro. Over 60 different Canon and Nikon digital SLR cameras are supported including Nikon Z series mirrorless up to the Nikon Z9.
Connecting up cameras is made simple, a USB to lightning connector may be required for some iPhones but otherwise a simple USB connection to the camera is all that's required. Completely wireless connectivity is also possible using the Reikan Wireless Camera module (available separately).
The FoCal Mobile App is now publically available on Apple App Store as well as the Google Play Store, the unpaid download provides Verify Setup, Sync Camera Time and AF System Check to really find out how well the connected camera is focusing.
With in-app purchase Full AF System Calibration allows users to calibrate camera auto focus and compare their personal calibration result with other FoCal users by using the FoCal comparison database.
More details on the Reikan FoCal blog https://blog.reikanfocal.com/2022/11/reikan-focal-mobile-1-0-released/.