A 70-year-old man got an unusual warning from his bed. The mattress, which tracked his heart rate through tiny body movements during sleep, had recorded an average overnight rate of 42 beats per minute, far below his usual 78.
The warning turned out to be real. Doctors diagnosed complete heart block, a serious failure of the heart's electrical wiring, and implanted a pacemaker. Cardiologist James Ip of Weill Cornell Medicine and NewYork-Presbyterian Hospital described the case in a December 2025 report in the New England Journal of Medicine titled "Complete Heart Block Detected by Consumer-Facing Digital Health Technologies."