Ukulele Tuner, developed by Aquarelah, is a free Android app that helps ukulele players tune their instrument. The app produces sounds for G, C, E, and A notes, making it easy for beginners and experienced players alike to get their ukuleles in tune.

The interface of the app is simple and user-friendly. Upon opening the app, the user is presented with four buttons for each note. Pressing any of the buttons produces the corresponding sound, allowing the user to easily tune their instrument. The app also includes a feature to adjust the frequency of the notes, which can be helpful for players who prefer to tune to a different pitch.

Overall, Ukulele Tuner is a great app for ukulele players looking for a quick and easy way to tune their instrument. It is especially useful for beginners who may not yet have a good ear for tuning. The fact that the source code is available on GitHub is also a plus for developers looking to build upon the app's functionality.