I want to Send AT Command to Android phone.
I know SDK does not support this.
but there are two solution :
- change the code of Kernel and release your new Android (it seems it is so hard!) 
- LoopBack on - USB.(i think Bluetooth is same)
About second solution , when you connect your phone to PC with USB cable , you will see a GSM modem on Device Manager that help you to send AT Command to GSM Modem.
If we find a solution to loop back on mobile phone , we can send AT commands to GSM Modem.
Question is : HOW to loop back and what tty file on kernel will help us?
 
     
    