Name: Tabata
Rating: 4.3 (148 reviews)
Author: Efflon

A timer app to record your Tabata workout or any kind of intervals. Easy to use, with advanced features to customize.
If you like this free app, please consider a small donation https://www.paypal.me/efflontabata
In the app, press 'menu' for settings.The app follows native apps behavior and records a .FIT file for you workout effort with a lap marked per interval and rest. Interval time, rest time, repetitions, sets, set rest time, activity type, warm-up/cool-down, countdown and GPS on/off are configurable in the app.

! Note: To change settings, first start the app on the watch, then press menu (on e.g. Fenix this is long press up). No settings are available in the Garmin Connect mobile app.
Sound and vibration follows the system settings (on e.g. Fenix Settings/System/Sounds)
    
On start, a configurable countdown (3s default) allows you to get ready before time counting starts.
When Warm up / Cool down is enabled; pressing "start", starts the activity and the warm up counter begins. "Back" ends the warm up and the configured workout begins. Once done, cool down begins and is ended by pressing "back".
During a workout, pressing "back" will skip the current interval or rest.
When GPS is turned on, a good GPS signal is marked by a beep and a green progress bar for a few seconds.
    
Note, the activity types on Garmin connect does not always map 100% to activities on other services (e.g. use Fitness in the app to record a "workout" on Strava).

Note, wrist based HR is not great when lifting weights or doing CrossFit like workouts, use a chest strap monitor for increased accuracy. 
   
For feedback questions etc use this thread: https://forums.garmin.com/developer/connect-iq/f/showcase/3172/app-tabata or click "Contact Developer" to the right.
    
Release notes:
0.0.19 Fenix8 and more missing watches (Special thanks to S.B.)
0.0.18 watches with 416x416 and 454x454 screens
0.0.17 fr255, fr255m, fr255s, fr255sm and fr955
0.0.16 Epix2 and Fenix7
0.0.15 Even more watches added.
0.0.14 New watches added.
0.0.13 Cool down bugfix and total time bugfix.
0.0.12 Configurable countdown. "Back" to skip interval or rest.
0.0.11 Minimal workout/rest time 2s. Total time shown when saving. Minor performance tweaks.
0.0.10 Support for fenix Chronos with firmware 5.80+
0.0.9 Fenix 5/5X/5S
0.0.8 Bug fix, GPS on/off
0.0.7 Added Warm up / Cool down
0.0.6 Stronger vibrations, larger fonts and more devices
0.0.5 Added sets and set rest time.
0.0.4 D2 Bravo added.  Now possible to set whole minutes (int/rest).
0.0.3 GPS support, laps per reps and D2 Bravo support.
0.0.2 First release