Please check if you have set the correct baud rate on your BT device. It must match the baud rate that you have set in your Arduino sketch in Serial.begin(115200). Note that with new Arduino boards you should go with baud rate 115200.
For the process stopped error it would be helpful if you post your LogCat of your Android phone so that we can see what caused the error. In your LogCat there is normally a much more detailed description of the error.