Trocks797 saidIf they have a clear, solid lock, they are crazy accurate. My app is so accurate it knows when I have quit running when coming to intersections, and it knows it quick too. Granted, I am speaking about Android phones, specifically the Droid, Droid X, Droid 2, and Thunderbolt. Those all have solid GPS chips. I can almost guarantee any other modern phone will too, including other devices. Check out this pic of me biking around the dorms (note the blue dots...pausing at intersections):
Long story short, it is accurate.
I think I can shed some light on this.
A wristwatch with a GPS receiver is at a disadvantage compared to an App running on a cellphone. The cell network electronics are still much bigger than a wristwatch. But the cell network can help you determine a fix quickly, especially if tall buildings prevent you from seeing more than one GPS bird.
Verizon, UsCellular, and Sprint: regular voice/data signals are GPS-synchronized to enhance network capacity for the IS95 standard.
Around 2007, that phone standard enhanced its ability to determine a fix if it can't see three GPS sat birds. AT&T/TMobile uses the European GSM system. They may have similar AGPS capabilities though.
Anyway, wristwatch GPS, better than nothing. Cellphones sold in the US must have E911 enhanced location accuracy so they can find you in an emergency.