Over at Macworld, TidBITS editor Glenn Fleishman explains Apple’s curious statement that GPS positioning would take minutes without its secret sauce of Wi-Fi network and cell-tower location data. Apple (and other mobile device makers) supplement GPS with several clever techniques to get a faster fix. follow link
Wake On Demand in Snow Leopard
Putting your Mac to sleep saves power, but it also disrupts using your Mac as a file server, among other purposes. Wake on Demand in Snow Leopard works in conjunction with an Apple base station to continue announcing Bonjour services that the sleeping computer offers.
While the requirements for this feature are complex, eligible users can toggle this feature in the Energy Saver preference pane. It's labeled Wake on Network Access for computers that can be roused either via Wi-Fi or Ethernet; Wake on Ethernet Network Access or Wake on AirPort Network Access for wired- or wireless-only machines, respectively. Uncheck the box to disable this feature.
How the iPhone Supplements GPS