What? That is AMAZING!! Thank you! That's why I hang around here. That is exactly what I needed.
Ha, cool! When you first said something about intervals, I thought that you wanted a timer that'll alert you when you need to start/stop your exercise (like Tabatas, for example), which is what I've wanted. Then I read your post again and thought, "Wait a minute... I think this'll work..."
For the OP's question about "must-haves", here's what I miss when I wear one of my regular watches:
- Temperature/weather
- Texts/calls when I leave my phone at the far end of the apartment
- Logging workouts
- Flashlight for walking around the bed and not stubbing my toes
- Morning alarm on my wrist
- Light weight (relatively speaking)
- Apple Pay and Wallet
- Simple games, like Rules and Alien Invasion
- Skim through emails and delete the ones I don't need
- Remote camera shutter for the phone
- Sports scores
- Laundry alarm (back when we lived in an apartment building with communal laundry)
- Navigation directions (a little redundant with CarPlay, but excellently valuable at every other time)
- Live weather radar (maybe not a "must have", but it sure is cool)
- Calculator
The true "must haves" were, for me, tight iOS integration, on-the-wrist comfort, good looks, simple operation, and robust third-party support. From the beginning, it was clear that Apple hit all five of these points better than anyone else, so choosing whether to try the watch at all was an easy decision.
EXTRA TIP if you haven't tried this already: Load up every single compatible app you have now onto the Watch, then try them out to see which ones are any good. My favorite example has been the variety of news apps. Of the five I've tried so far, each of them approach the platform differently; and it became obvious which ones knew what a smartwatch is best for, and which ones either didn't care to do anything or tried to make it do too much.