The smartwatch's Blood Oxygen app lets you measure the oxygen level of your blood on-demand. It's been MIA for more than a year thanks to a patent spat, but it's back in action now.

The feature was removed on select smartwatches due to a patent-infringement lawsuit, but Apple has “redesigned” it.

The company said it would issue a software update to restart the technology, which was caught up in a patent dispute.