Unless I'm mistaken, the watch and Mac have all the hardware to make this work. And Apple lets you access your credit cards with just the watch so they are pretty confident in its security. The watch also works with handoff on the Mac, so it definitely can interface with the computer. It would be amazing if Apple let the Apple Watch unlock the Mac. It would work by not requiring a passcode to unlock the Mac if the watch is within 6 inches of the Mac. Would save so much time and be a killer feature for both products.