Skyhook is no-way exclusive on the iPhone. You can use it in your Android or WinMobile app, I think it's included in the Droid, and it's in other Wifi products.

GPS and tower triangulation make location by WiFi not as useful on a phone. Phones by law have to be able to know where they are (for e911) and a WiFi database doesn't meet the level of accuracy.

Tower triangulation is really just not very precise (at the moment). If I'm in an area with no wi-fi networks and attempt to get my position without GPS, then I'm given a pretty huge range of coordinates I can be in (at least a square mile). If I give it enough time, AGPS can kick in and get me closer, but if I am in range of a couple of wi-fi networks, I'm usually within 50-100 feet or so in a couple of seconds. The majority of APs seem to be in Skyhook nowadays. I understand why Skyhook can't be used for e911 — APs can move, or the information can be inaccurate from the start. So, in that respect, AGPS is more accurate, but not as precise. In my daily usage, precision is more important to me.

WiFi location is fast and works indoors and in the concrete jungle, that's the advantage. It may not be accurate but it could be self-correcting - the iPhone could feed info back into the skyhook system about the location of a new hotspot after it gets the call tower and GPS info.

I have no proof that it does, but I have an anecdote. The first time I plugged in my WiFi point at a new address, the phone connected and thought I was at the old address - until 5 minutes later when if shot me across the country. Never happened again.

So why do you think Apple use WiFi positioning on the iPhone?

GPS can take minutes (or never come back with a location if you are inside) and tower triangulation has never lived up to the accuracy claims that they made.

It's a nice backup and is very useful in the iPod Touch.

citation needed