This smart ring is quite impressive. I downloaded the recommended app and found it very easy to use. The first night I had a pretty high heart rate at one point just before bed, I checked the app, and sure enough my rate was elevated. It actually scared me, and I thought the ring may be wrong. I double checked the rate against my oximeter ~ it matched both heart rate and blood oxygen levels, which gave me some confidence on accuracy. If I had any other symptoms or questioned what readings meant, I would definitely contact a physician. Only a doctor can make an accurate diagnosis. I also have a blood pressure monitor to double check any issues.After that night, I had some good sleep, tracking the progress in the app. I had gotten up in the night, and it was tracked, for example. Heart rate & blood oxygen were measured in timely increments and recorded throughout the night. Sometimes you can also see either a red or green light flash as measurements are taken.Speaking of measurements, I got a size 10 for my pointer finger. It took some getting used too, but I didn't really notice I was wearing it after awhile.The app also tracks calories burned and excercise progress including steps walked. So far, I'm impressed with this ring ~ and the price is right!