GymTimer by FRDM

GymTimer is a stand-alone app made exclusively for the Apple Watch to help you keep your intervals under control, so you can focus on your workout!
You can set how many minutes or rounds, and how long you want to work or rest.
The app is using a combination of sounds and vibrations on your wrist to notify you when it is time to rest, work etc.
Three different timers included:
•AMRAP (As Many Rounds As Possible)
•TABATA
•EMOM (Every Minute On the Minute)
Made by gym-goers, for gym-goers!

GymTimer uses HealthKit to be able to show you, your heart rate during your work outs, and to keep the app active while you use it.