The US Food and Drug Administration (FDA) has just granted the first ever clearance for an Apple Watch accessory to be used as a recognized medical device. Obtaining the green light took just over two years, around a year longer than the company had hoped.

AliveCor’s Kardiaband EKG reader is a Watch band that provides a much more convenient and discreet way to obtain an EKG reading, which can be used to detect abnormal heart rhythm and atrial fibrillation (AFib) …

Obtaining an EKG reading is as simple as touching a sensor on the Watch band for 30 seconds.

Technically, the heart-rate sensor built into the Apple Watch could do the same thing. However, Tim Cook has stated in the past that Apple doesn’t want the Watch itself to be subject to FDA approval as that could slow down the pace of development.

AliveCor CEO Vic Gundotra told TechCrunch that FDA clearance is the difference between simply alerting you that your heart-rate is unusually high – which Apple is allowed to do – and providing an actual diagnosis.

The Kardiaband costs $199, but requires a $99 AlivCor annual subscription to unlock full functionality.

EKGs are usually only available in offices and hospitals — and only after a life-threatening event. Having one on your wrist that you can use to check your heart and then send a readout straight to your doctor is vital to prevention of a heart attack or stroke.

And, as Gundotra also points out, “It’s not possible to diagnose atrial fibrillation without FDA clearance. That is a big, big play.”

A recent study showed that the Apple Watch is capable of detecting sleep apnea with 90% accuracy and hypertension with 82% accuracy.