Official App from Future Motion
An official app from Future Motion is available for iOS and Android. Onewheel and Onewheel+ are supported. In addition to being able to choose digital shapings, configure settings and monitor your board status, the app includes GPS functionality for mapping your rides, finding and messaging other riders, and a leadership board tracking top speed and mileage.
With the introduction of the Onewheel+, Future Motion bought OWheelBuddy- a paid app which author Florian Geymayer has since discontinued. Previous purchasers of the app can still download it from Google Play. It has similar functionality to the official app, but without support for Digital Shaping 2.0 from the Onewheel+. Some users find this app to be more lightweight, and work better on older devices than the official app.
Onewheel Web Test by Drew Baumann (Github) retrieves basic statistics (including battery level, odometer reading, ride mode, serial number, and revision) from your Onewheel- all via a desktop web browser (Web Bluetooth support required).
pOnewheel by Kevin Watkins (Android Google Play Store) focuses on extended and hidden statistics (including pitch and roll). It has been open sourced on GitHub in the hope that the community will enhance it further. In addition, you can now enroll in a beta version to get new updates, including support for Onewheel+'s Digital Shaping 2.0.
onewheel-video-hud by Walther Maciel (Github) is a python script that can read log files generated by pOnewheel and add a dashboard overlay to videos you've shot on Onewheel.
OneWheelWear by toothR&D (paid version: Android Google Play Store free, feature-limited demo version: Android Google Play Store) is an app for Wear OS (formerly Android Wear 2.0) devices supporting Bluetooth LE. It is under active development. A Facebook group exists for application support.
The first suggested fix if you're having problems with one of these apps is to try uninstalling and reinstalling it. You can also try clearing the application's data.
If you have an older Android device and the app is running slowly, you can also try to boost the general performance of your phone by limiting the number of background tasks it can keep open, but this requires enabling Developer Options (Settings->About Device->Software infromation->Tap build number 7 times). Then, Settings->Developer Options->Limit background processes->At most, 4 processes. If it doesn't help, you can always switch it back to the Standard Limit.