When Apple finally announced the Apple Watch smartwatch last October, many in the healthcare space were a little underwhelmed. The killer health device that a slew of recent hires had led us to expect was nowhere to be seen, with Apple opting instead for a flashy device that doesn't track any more than what available fitness trackers already cover.

The Wall Street Journal published a report that offers some rationale for the discrepancy: Apple initially planned a much more ambitious health device, but concerns around accuracy and regulation stymied those plans.

The Journal wrote in its report: "It’s not unusual for Apple to experiment with many technologies or shift focus during product development, but the watch was especially challenging, people familiar with the matter said. Internally, the project became known as a 'black hole' sucking in resources, one of these people said."

They report that the development of the Watch began in 2011, and at various times plans included skin conductivity sensors, EKG sensors, blood pressure, and blood oxygenation. The conductivity sensor displayed inconsistent readings in cases of hairy arms, dry skin, or when the watch was adjusted differently, while the blood pressure and SP02 sensors sparked FDA concerns, in addition to being inconsistent. 

Over the course of the Apple Watch development, news broke of Apple hiring away experts from various digital health companies: Michael O'Reilly from Masimo, Nancy Dougherty (who had previously worked at Proteus Digital Health) and Ravi Narasimhan from Vital Connect.

The Wall Street Journal story doesn't tie up every loose end, though. No mention is made of either sleep monitoring or blood glucose sensing, and Apple hired experts on both prior to the Apple Watch announcement: Ueyn Block from C8 Medical Sensors and Todd Whitehurst from Sensionics both worked on glucose sensing, and J.E.M. Raymann, formerly of Philips, has a strong background in sleep sensing.

We've already speculated that sleep got the ax because of battery concerns, and glucose looks like it will be trackable on the Apple Watch, just not via Apple Watch's built in sensors. Dexcom has confirmed that it will have an Apple Watch app available when the device launches that will talk to the receiver connected to a Dexcom continuous glucose monitor.

It's likely that Apple's scale down from medical device to fitness tracker was already underway by February 2014, when MobiHealthNews spoke to sources familiar with the project. They told us to expect a simpler suite of health tracking features than what many in the industry were predicting at the time.

The Wall Street Journal story concludes by noting that Apple Watch's advanced capabilities may not be shelved permanently, and could surface in a future update of the device.