Your phone camera might have another useful feature beyond taking selfies. Engineers at University of California San Diego and the University of Washington published a proof-of-concept study that showed a smartphone was capable of detecting blood oxygen levels almost on par with the industry standard medical device. If you’ve ever gone into surgery, you’ve likely had a pocket-sized device, a pulse oximeter, clamped onto your finger to track the percentage of oxygen in your red blood cells. This kind of oxygen monitoring was especially useful for triaging patients with acute respiratory conditi…