A simple bluetooth module like a HC-05 wired to your Arduino will give you a serial stream that can be read and/or written.
With the RX/TX connected to say pins 10 & 11, a SoftwareSerial() object will provide access:
SoftwareSerial mySerial(10, 11); // RX, TX
value = mySerial.parseInt();
If you connect the module to pins 0 & 1 - you can just use the Arduino standard Serial functions, but it will cause problems uploading to the board. In which case you would disconnect the bluetooth module for uploading.