I think you might need to review the concept of "wireless." Specifically wave frequencies that technologies use.
A GSM or CDMA modem is very different than a wireless ap. Also, it means that the people using it will never be able to connect to you, and you will not even know that they are using it unless you have the equipment for sniffing cell phone communications.
This thread is very convoluted but it seems like you want:
Jasager - to make others connect to you
Some way to track these people who connect to you - Finding the location of people who connect to you is theoretically possible if they don't move, never change IP addresses, and don't change their MAC address. Good luck finding this ethereal person.
Zipit - for hacking someone else's wifi
A way to triangulate the wireless ap that you break in to so that you know where it is - The variation in the wireless AP signal strength will pretty much kill triangulation efforts... unless you are planning on spending some time near it...
GPS - because it was the subject of your original post
TL;DR - This is the most diverse assortment of technology I have seen in a 10 post thread, and there is no real connection between them other than the words "wireless" "modem" "AP" and "GPS"
