After looking at LeJOS source codes we found that when you are trying to pair with NXT device controlled by LeJOS it always sends "1,2,3,4" as a code. So if you pair a mobile phone with NXT using standard phone menu and entering 1234 as a code, you will then freely connect after that to robot.

My collegues started to implement mobile phone application and a program for robot. We decided that robot will be able to do very simple unary commands, such as "start motor rotating forward, use motor A" So each command will have two parts: 1) what to do with motor and 2) which motor to use. So if you want to make robot move forward, you should send in our case to commands: "start rotating forward motor B" and "start rotating forward motor C". This approach will allow using the same LeJos program to controll different NXT robots and all that you will have to do is to change command combinations which are sent by mobile phone. Also we are going to sent data from sensors back to phone, so that you can see values at sensors while you are controlling your robot.