As the app says: iWatch does not record body temperature
Yes the app works, but can’t actually measure your body temp (the watch doesn’t have that capability). So don’t complain it doesn’t work. Read the app info. Yes, I was disappointed to learn the app is only a place for you to record your body temp. Just like the blood pressure or blood sugar recordings. You need an external device to collect the data, then you manually enter (record) your findings in the watch app.