The Apple Watch was originally planned to be focused much more on health-monitoring, according to a new report, with an array of sensors for tracking blood pressure, heart rate and other vitals. Challenges with deploying the sensors, however, meant that Apple had to focus on notification, transaction, remote control, and other, more rounded features as well. The Wall Street Journal:

Development languished because much of the health-sensor technology failed to meet Apple's standards, these people said. Apple tinkered with sensors that measured the conductivity of skin, a concept used in polygraphs to gauge stress. The technology also showed promise for heart-rate monitoring such as an electrocardiogram, or EKG, these people said.

But these features didn't perform consistently on some people, including those with hairy arms or dry skin. Results also varied depending on how tightly the person wore the Watch, they said. Instead, Apple opted for more pedestrian pulse-rate monitoring, these people said.

The report went on to add that future iterations of the Apple Watch may include a few health-related sensors. Meanwhile, the Apple Watch as it currently stands looks to focused on convenience as its killer feature.

As for production numbers, they report that Apple is looking to manufacture around 5 to 6 million units in time for its launch. That number would be considerably higher than the 720,000 shipments of Android Wear devices in 2014. The report suggests that half of the production run is for the entry-level Apple Watch Sport, which will be priced at $349. One third will be the stainless steel Apple Watch. That would leave the remaining one-sixth of the production run — which comes out to around 850,000 units — for the gold Apple Watch Edition.

The Apple Watch launches this April.