Timewave is an app that allows you to create flowing timers, i.e chains of timers that fire one after the other. You can create workouts, cooking timers, pomodoro timers, etc. The app also features a full Black & White UI.
First thing that went through my mind was "hmm, i can use this as a workout timer". I know there are some apps that focus specifically workout timers, but this looks that it can adapt to whatever the user needs.
Let's give it a try.