Hi There! There are still a lot of iPhone 3 Gs out there, and especially their owners might be unhappy about the GPS accuracy.
They can be helped with an external (Bluetooth) GPS receiver such as this one:
However, I own a Holux M-1000 which I had purchased to use with a NOKIA phone. I was quite happy with this device and would be happy to use it with my 3 Gs.
I thought that the iOS blocks external Bluetooth devices or decides which device the iPhone is allowed to pair with. email@example.com, however, tol me that it is down to the manufacturer of the Bluetooth device to make it accessible for the iPhone.
I wrote an e-mail to Holux customer support and received the following answer:
Have a nice day. Sorry, Holux GPS receiver is not compatible with Apple series product. We ever tested."
Aah, right. Is anyone interested in a Holux M-1000, used, good condition?