The new Series 4 Apple Watch has several unusual new features in addition to the anticipated larger screen, including a heart rate monitor capable of taking an electrocardiogram (ECG) and another that detects falls.

Disclosed at the Apple event life streamed from its Cupertino, California headquarters,  the S4 Watch is two times faster, has a 30 percent larger display, is swimproof, and has better speakers. It has a new dual-core 64-bit processor with 18-hour battery life, six-hour outdoor workout life.

Apple said the new fall detection feature “Requires a tremendous amount of data and analysis. We learned that with falls, there is a repeatable data pattern.” If a wearer is motionless for more than a minute, it automatically calls emergency services.

The U.S. Food and Drug Administration approved the S4’s built in electrocardiogram feature, which will save results to a PDF so they can be provided to the wearer’s doctor.

It is the first over-the-counter device capable of taking an ECG. Built-in electrodes on the back and crown detect electrical impulses from your heartbeat and it will send them to the S4 chip. It takes 30 seconds, and then you get a heart rate analysis. It can detect atrial fibrulation in people who don’t know they have the condition.

The S4 starts at $399 for GPS, $499 for cellular, while the S3 will cost $279.  S4 is available Sept. 21 with preorders starting Friday. Watch OS5 is available Sept. 17.