communication between mobile phone and server computer

Hello!

I'd like to create such an application that the user of mobile phone can call special service number and would connect by calling this number to the server computer in building about one kilometer from him/her. This is situation if that person has got his/her mobile phone from boss.

In the case if it is private mobile phone, I'd like that person to call the special service number and stop connection just after connecting. Then the server would call back to that person.

The puprose of this connection is to send voice data from employee and save this data as wave file on the server for further analysis.

I thought about using Java language. I would create application for two or three the most popular kinds of mobile phones. (What are those?)

Can you give me any suggestions / inform about useful technologies which I can apply in this solution?

Thanks very much for your help!

Greetings!