Floating Timer lets you create custom workout timers that stay floating on your screen, allowing you to keep track of your progress while using other apps.

If you have any feature requests or bug reports you may send them in here: bitbucket.org/newplan/floating-timer/issues
From version Floating Timer 0.5.180923 (Unreleased):
Updating to comply with Google Play requirements
Preparations for Android Oreo support
All versions