I have to confess that I'm not often amazed by something electronic - this is my line of work, after all. But I turned on my new Apple iPod Touch and idly started up Google Maps. The bottom left-icon looked like a 'My location' icon, but, knowing that this was an iPod Touch and thus had no telephony and no GPS, was actually quite surprised when it defaulted to a map of the UK. Heh. At least I didn't have to spin a globe to find my country.
I tapped the icon, expecting to be taken to the centre of London, or similar (it's our capital city etc). I was GOBSMACKED when I was zoomed in to the right spot on the right road, EXACTLY where I lived.
Magic. Had to be. How the ******** did the iPod Touch know where I lived? Had it somehow absorbed the information from iTunes, which in turn had somehow cribbed it from something else on my PC? I took the Touch outdoors and went for a walk. The My location crosshairs FOLLOWED ME. Arghh... HOW?
As far as I can tell, the Touch's (and the iPhone's) My location feature is not only tied to cell ID and (in the 3G version) GPS, but is ALSO (and, in the case of the Touch, the ONLY method) derived from a global database of home Wi-Fi networks, run by Skyhook - here's a 'How it works' page. Apparently it's self-healing, in that errors and additions are automatically handled by the system and the database updated.
So, by working out which Wi-Fi networks I was nearest and by triangulating from their signals, the Skyhook system was able to get me to within about 5 metres. Really impressive.
Of course, Skyhook's system falls down completely when out of suburbia, but still, it had me puzzled and bemused for half an hour and all credit to the creators and integrators.