This is the official recommended mission planner for INav on the Google Play Store:
From the official GitHub repo:
Mission Planner for INAV can be downloaded from the Google Play Store. There is a free version which limits number of waypoints to 5 and (very reasonably priced) paid-for version with additional functionality. The application is not open source. For questions and help the RCG "Mission Planner for INAV" thread can be used: RC Groups support forum.
There used to be an app for iOS as well, but this is no longer available on the app store.
Another app for Android is Droid Planner 2:
Droid Planner 2 can also be downloaded from the GitHub. It is free and released under GNU Public License v3.
Droid Planner only supports iNav's one-way MAVLink protocol. The following telemetry data is displayed:
Vehicle position on map, active flight mode, heading, altitude, speed.
A broken connection recovers once restored after any amount of time. The flight track remains on screen even when data link is broken -> lost model recovery. Log files can be opened in PC software Mission Planner.
More options can be found in the GitHub repo.