Touch Bar Timer is a little stopwatch for your Mac’s touch bar.
Tap to start/stop
Double-tap to reset
Hold to open the app preferences
More background: https://www.alexzirbel.com/touch-bar-timer
It's also open source! Thanks to Pixel Point, whose "Mute Me" app was the starting point for this project.
The platform for plugins and customization for the Mac touch bar
Drops is a piano accompaniment app with a computer keyboard.