Hiyd is a health tracker that attaches to the watch you already wear

A startup called Hiyd has built a tiny health tracker you stick to the back of your own watch. It is a slim disc about 2.7mm thick that weighs just 7 grams. Hiyd says it can measure heart rate, sleep, movement and calories. The disc uses microsuction, a textured sticky silicone that holds on without glue. It leaves no marks on the watch. The data syncs to an iOS or Android app. Hiyd founder Salah Batroukh said he wants health tracking to be invisible.

Many people dislike fitness trackers because they look bulky. They do not want to swap a nice watch for a plastic band. Hiyd is trying to solve that problem with a clip-on sensor. The team films people walking, jogging and running to train its AI to read movement. The app also plans food tracking. Instead of counting calories, it will point out links between habits, sleep and workouts.

Health trackers can help people spot problems early. A device that fits on a normal watch could get more people to check their health.