I'm really glad to have this ECG test on the watch. Yesterday morning when I was letting the dogs in at 4 am. I noticed my watch was showing a heart rate in the 120s, and varying a lot. I took this test, and found that I was in afib. I'm currently in the hospital getting checked out for it, but glad to have gotten the advance notice, because I had no other symptoms other than the high heart rate. Thanks, Google!