A paper presented at Heart Rhythm Society's Heart Rhythm 2017
conference by Gregory Marcus, professor at UCSF, describes the
results of using an Apple watch together with application software
developed by Cardiogram."DNN solution" means the application software.When compared against a 12-lead electrocardiogram reference, the resulting Apple Watch and DNN solution was found capable of identifying AF with an accuracy of 97 percent, sensitivity of 98 percent and specificity of 90.2 percent, all high marks compared to past detection algorithms.
"AF" means atrial fibrillation.
For the details read this article at --> Appleinsider.
This seems like good progress in developing health monitoring
applications for the Apple Watch and other smart watches.
Presumably the current Cardiogram application for Apple Watch
currently available from iTunes does not yet implement this atrial
fibrillation detection scheme.