Question : How does GPRS work?

Can the following be done in j2me:

capture from the microphone voice input, encode it in realtime  (aac,mp3 low quality - 16-24kbps), encrypt it and send it to another phone via gprs while the other phone is doing the same thing?
ofcourse the receiving phone will decrypt and play the voice data to the phone speaker.

how can i see if a phone is connected to the internet via gprs(is online) and how to send data to it (not trough wap push)?

Basicly i'm thinking to develop a software that sends encrypted voice trough gprs protocol and i'm wondering if it's possible.

Answer : How does GPRS work?

Yes its possible..When the MS is connected using GPRS it will get an IP addres..So if you can speak to your Telco then thats the easiets way..otherwise you can enable the MS to connect to gprs always and use the msisdn..
But the basic issue i can see is as far as i know (atleast in this region of east sideof the planet) i dont see any MS having the capabilities of encryption/decryption...???