Key Mapper

Key Mapper is a free and open source Android app that can remap your buttons and fingerprint reader gestures. The aim of this project is to allow anyone to map their buttons in any combination to anything.
The original application is by Seth Schroeder, better known by sds100.
It's development was started in 2019 while Seth was still in high school. It was really more of a pet than a product. Now it's evolved into the best free, libre, and open source key mapping Android application, with over one million downloads in the Google Play store. As of Febuary 1st, 2023, The app has an average rating of 3.8 stars from over 15.7 thousand reviews.
As stated in it's GitHub page, the applicationis free and open source. The Google Play page even states that no data is shared with third parties, and that no data is collected at all.

Unfortunately, Seth has had to dedicate more time to school and work, leaving Key Mapper unmaintained. The official note stating this was posted to the Key Mapper Discord at the end of 2022.

Well, working on this project was a fun ride! This project has taught me so much about Android, software development and how to collaborate with an online community. It has been my dream to lead a big FOSS project with people from all over the world so a huge thank you goes to everyone that spread the word and helped on GitHub along the way. Unfortunately, I do not have any more time to work on this project - I'm now studying Computer Science at university and I have landed software-dev side jobs, which has taken up any free-time I did have to code on the side.

A special thank you goes to everyone in the Team for their long-term committment to the project and for being so engaged with the community. The Discord server, website and app store listing will still be up! So don't worry, you can still map your keys to your heart's content.

sds100, December 11, 2022

However, even though Seth is done with development for now, that doesn't mean you can't help keep it going. Due to the nature of open source, you can make changes to the Key Mapper code yourself. Maybe Seth will see your awesome code and make it part of his own!