Dear Andy,
I am new here and I have some questions to ask you about. I have just started with my school project (bus tracking system). My part in this project is to interface GSM using a microcontroller and to a computer (receiver part). I have some ideas but not good enough. This thread will be a part of my research. Could you please give me some basic ideas how about to do this?
Have you looked at Wavecom: their devices allow you to write 'C' firmware within the module - so no external microcontroller is required. http://www.wavecom.com/OpenAT
Other manufacturers also have various options for scripting within the module...
"One thing in my head is to use a ATMEL microcontroller."
That's a bit like saying, "I'm thinking of using a Ford car" - Ford makes a whole range of cars!
Atmel make (at least) three different families of microcontrollers: 8051, ARM, and AVR. Which did you have in mind?
"I want to find out if there are any other devices I can used?"
See above - do you even need a separate microcontroller at all?
Interfacing to a modem (any modem, not just GSM) is really just a serial comms project - just about any microcontroller could do it (GPRS is more complex, as it requires TCP/IP).
"which product Keil can offer me to use?"
It should not surprise you to find that this information is on the 'Products' page! http://www.keil.com/product/
Again, this has nothing to do with software development tools - any compiler from any vendor will do. First, you need to decide which microcontroller family (if any) you will use - then you can look for tools which support that family!