Also you need to be able to talk to the cellphone, usually AT command.
Get the latest command set of the net.
Also you need to talk to the gps somehow, some makes have propriety languages, but there are standards as well.
Decide on your module but check what languages it speaks, and research each a bit to see which you can live with.
Then you need to decide what mcu will be able to handle everything you throw at it. If you want to go 1sec update intervals, get something above entry level.
I could tell you more about the languages, but I can't remember for some funny reason, my gps stuff is also archived somewhere off-disk.
ublox is also quite nice, there's trimble, although everyone I know have moved away from it.
Are you going to use a hand-held cellphone, or module? That can determine your mcu as well since you have to connect to it somehow.
Or are you using a PC to talk to everything, then you need a programming tool/dev suite, or whatever you want to call it.
It can be a big project. Sure you want to do it?