Arduino Bluetooth Breakout Board
The Adafruit Bluefruit LE (Bluetooth Smart, Bluetooth Low Energy, Bluetooth 4.0) nRF8001 Breakout allows you to establish an easy to use wireless link between your Arduino and any compatible iOS or Android (4.3+) device. It works by simulating a UART device beneath the surface, sending ASCII data back and forth between the devices, letting you decide what data to send and what to do with it on either end of the connection.