Halo

An iPhone and Apple Watch app by Han Kim

Apple Health has years of numbers from your watch and almost no opinion about them. Resting heart rate 61. OK, is that a lot? For one person it's a great day and for the next it means they're coming down with something, and the Health app can't tell you which one you are.

So that's what this does. It goes through everything your watch has recorded, figures out the range each measure normally stays in for you personally, and then draws today on a ring with one dot per measure. Dot on the band = inside your usual. It takes about two seconds to read.

Nearly every day the answer is "Steady." The interesting days are when a few of the night readings (heart rate while asleep, breathing rate, wrist temperature) go off together and don't come back the next night. Then it says "Something has shifted", shows you the ones that moved, and keeps an eye on it until you're back in range.

Nothing leaves the phone, there's no sign-up, and I don't run a server for it. Also it's not a medical device. It has no idea why a number moved, it just notices that it did.