Everyone knows that the Apple Watch can measure the wearer’s pulse, using inside the four rings on the back of the watch. Normal heart rate monitors rely on skin conductivity, but Apple took the Apple Watch in a different direction, instead using infrared and visible-light LEDs along with photosensors. Pulse tracking may be useful for exercisers, and Apple has made much of how you can send your heartbeat to a loved one.
But if it struck you that Apple must have larger plans for these sensors, you’re not wrong. The question is not what the Apple Watch can sense, but what can be determined from what it does sense. What causes your heart rate to increase, apart from exercise? Try stress.
The first indication that Apple has something up its sleeve came in the form of a quickly deleted tweet from model and runner Christy Turlington, Apple’s poster child for using the Apple Watch in her marathon training. She wrote that her Apple Watch accused her of lying about how a long run had gone.
Accused her of lying? Discussing this with a long-time Apple developer who wished to remain anonymous revealed hints of a private API in the Apple Watch software development kit. Currently available only to Apple, the API goes by the name TruthKit, and returns a range of values that report on the delta between the current and recent past heart rates, among much else.
It sounds as though Apple is using the Apple Watch’s sensors as a mini lie detector, not so much to rat you out to your spouse (since it was on Turlington’s watch, not her husband’s), but to help you realize when you’re playing fast and loose with the truth.
But perhaps Apple will make it possible to share that information with trusted parties, much as you might share your location with your spouse via Find My Friends. It’s the ultimate statement of trust — your Apple Watch could prove that you’re telling the truth about not chatting up your ex-girlfriend on Facebook. The question is if TruthKit will ever be made available to developers, so apps could tell when you’re stressed while using them. How long before the first mood ring app extends itself to the Apple Watch?
The real win might come with Apple Pay, which already offers industry-leading security when it comes to storing and transmitting payment information in a way that can’t be compromised. Where Apple Pay is having problems, though, is with stolen credit card numbers being registered into the system (see “,” 18 March 2015). If the Apple Watch could transmit a “confidence score” of stress related to a transaction, banks would be better able to identify fraudulent transactions.
Of course, such a system could run afoul of false positive stress from other situations. Imagine someone using Apple Pay to buy a wedding ring — an expensive, meaningful purchase. It would be entirely understandable if such a purchase resulted in an increased heart rate without there being any intent to deceive.