Activity++ was released this past week and is my favorite Apple Watch app I have downloaded in a long time. It's a very simple app, but one that builds on and improves the standard Activity app in a few useful ways.
First, I love the UI. It's a little busy, but it lets you view your activity data better than the standard app at a glance. I especially like how it shows e my current streaks for my move, activity, and standing goals. Tapping on any day in the list gives you a 24 hour summary of when you were moving.
On the topic of streaks, Activity++ has an option for "rest days." This means that if you achieve your goals 6 days in a row, you can miss your goal on the 7th day and not break your streak. This is really convenient and works with how most people live. This is the equivalent of a cheat day on a diet, and it's a welcome addition.
Finally, there is a stats page that shows you your average daily total for all 3 major stats, when your you had your best day, how often you hit each goal, and what your best streak has been. There's also a eat map so you can see what part of the day you tend to get the most activity.