To activate Google Now, I have to be on the home screen, to activate Cortana, I actually have to be in the Cortana app...
I guess this is one of those ‘if everything was perfect’ scenarios. A cool trick, that’s about it.
It's a cool trick. . . and requires exact conditions to work.
Obviously they are broadcasting a modulated radio signal at just the right frequencies and amplitudes to be picked up on the headset cable.
For people unfamiliar with the technology, microphones like the one in a corded hands-free headset convert audio (sound waves) from you speaking into electromagnetic waves. This signal is then sent down the wire to the device.
Because your voice naturally rises and falls in intensity and our voices cover a (admittedly small) frequency range this signal is modulated both in amplitude and frequency. Fun stuff for a tech guy like me. ;-)
Well, that wire (wires actually), running from the mic to your phone *can* act like an antenna and pick up electromagnetic energy broadcast at it. Your phone wouldn't be able to tell the difference from that or EM energy coming from the mic.
All good in theory and apparently they were able to gin up a test rig and demonstrate it. However... I'd be very interested to know the details of the headset cord and any modifications they did to it. I believe - though I haven't researched it - that any decent headset is going to use a twisted pair wire scheme. This is a simple and effective way to cancel out EM interference. With twisted pair wiring both the conductor and it's ground/return line are literally twisted around each other. That way any EM signal that is incident upon them conducts onto both equally. If both conductors get equal signal, it cancels out and there is no net/resultant signal on the wire. A wildly simple and effective technique engineers have been using for decades.
So they must have specifically selected a headset cable that does not use twisted pair wiring. (if such a beast exists) or they may have intentionally damaged (ie. cut) one of the conductors to unbalance the signal.
Short version is, I'm not worried. I'm going to keep using my headphones at the gym when working out, and keep trying to remember not to sing out loud. ;-)
to activate Cortana, I actually have to be in the Cortana app...
It can be voiced activated, but it’s so difficult I don’t bother.