More for general purposes, here is the list of all of the Garmin watches that use RefSix.
Add creative apps, watch faces, music and more to your Garmin devices with the Connect IQ Store app.
apps.garmin.com
There are a lot of HIIT/interval timing apps on Apple Watch, or you can set up intervals in the native Apple exercise apps as shown in the link below (Look for the Customize a Workout section in the link).
Choose a workout, set goals, and view results on your Apple Watch.
support.apple.com
I've used Refsix for a couple of years, but I think I'm going back to the
Referee Watch app by Winder on my Garmin Fenix 7. I always have the best of intentions of just using R6 as a timer and then updating the match record following the game, but I never seem to get to that. I LOVE it for the timing and heat map features, but I've tried to keep a match record on the watch and just can't get comfortable doing it. I'm tech-forward, but still like to keep a match record in written form. I think even if I started using an Apple Watch Ultra (which I'm considering after my current Garmin ages out), there are some other timing apps that seem to work well without the full match record features of R6.
If R6 could provide some sort of "easy" functionality where I could just enter cards and goals so I can get the time and location without doing any sort of extra recordkeeping (i.e. "Blue goal", "Red caution", "Blue send-off"), that would be ideal for me. I spend too much time messing around with my watch if I keep the game record on my watch, particularly when I'm in the center. It's not quite as bad to operate when I'm an assistant referee.