- Fantastical Calendar
- Carrot Weather
- Streaks (habit tracking)
- Things
- Lose It (Which I should be using at the moment, but I'm not)
Fantastical Calendar and Carrot Weather are pretty much always complications I have set, and both of these apps offer some great options for what to display on small and large complications. Things is not my favorite task manager (that title currently goes to Swipes), but it used to be my favorite. The fact that it offers a complication made me take another look. It's a solid task manager, and the complication is great if you are good about keeping your list of items to do Today reasonably short.
I usually have the Activity Rings set as a complication, and also frequently the timer, but those aren't third party
Sean
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I haven't tried Lifesum, but the Lose-it complication and app work fine on my watch. If you haven't tried in a long time, give it a try using the latest Watch OS and the latest Lose-It app. Restart your watch and your iPhone if you're still having problems.