It is!
With a UV sensor you can actually tell when someone is outdoors in the sunlight. The MS Band's sunscreen experience was tailor made to automatically remind people to reapply sunscreen when needed, but it was a fair bit smarter than just a simple timer. I have a blog post about it at https://meanderingthoughts.hashnode.dev/cooperative-multitas...
The important bit is the Band knew if someone was in the sun for an extended period of time (15 minutes) and then popped up a reminder to put on sun screen, and also then prompted them if they wanted future reminders. If opted in, the timer popped up at whatever interval they asked for (ranging from 1 hour to 4 hours in 30 minute increments IIRC).
But if the person stepped inside for more than 10 minutes (e.g. went to eat, entered a movie theater, but not just going to the restroom) the reminders automatically stopped. Another 15 minutes of continuous exposure would then restart the experience again.
It wasn't an ideal setup, since you should put on sun screen 30 minutes or so before sun exposure, but it was really helpful and families loved it.
The entire "experience" was just a single dialog (How often do you want reminders? Not at all, every hour, every 90 minutes, etc) but the logic underneath was designed to ensure it wasn't intrusive and that it only came up when relevant.
