I’m sort of amazed we’ve made it as far as we have without these two features being built in:
Sick days. Sometimes we get sick! It would be pretty great to not lose a streak because I have a really bad cold.
Rest days. This is the big one. One day a week, it would be nice if my calorie goal could automatically be a little lower. It’s very common for workout programs to have a day per week that is to be at a lower intensity.
There’s almost certainly apps that can incorporate this somehow – although I’m not sure how to reset the calorie goal for a single day, one assumes there’s an API for it.