RR Guitar Fretboard Trainer is a free Android app developed by Red Rabbit Software Inc. that aims to help guitar players learn the fretboard while away from their instrument. The app works by prompting users to find and identify notes on the guitar fretboard.

One of the most significant features of RR Guitar Fretboard Trainer is its ability to track user progress and generate new games based on the user's trouble spots. The app also includes customizable game profiles, right and left-handed fretboard options, and the ability to choose between standard 6-string guitar or any number of strings from 4 (bass) up to 10 strings. Additionally, users have the option to add sound, customizable alternate tunings, and explore the fretboard in full-screen or scrollable mode.

Overall, RR Guitar Fretboard Trainer is an excellent tool for guitar players of all levels. Its user-friendly interface, customizable features, and progress tracking make it a great app to have on hand for learning and practicing the guitar fretboard.