This is the latest Arduino BT microcontroller board supplied with the ATmega328 and the Bluegiga WT11 bluetooth module.
It supports wireless serial communication over bluetooth. It has 14 digital input/output pins (of which 6 can be used as PWM outputs and one can be used to reset the WT11 module), 6 analog inputs, a 16 MHz crystal oscillator, screw terminals for power, an ICSP header, and a reset button.
Arduino! Without wires! Plunk it down, turn it on, pair it to your bluetooth-enabled host, and you're tapping directly into your Arduino like it were cable tethered.
Because it is "mobile friendly" it offers the handy feature of a DC/DC converter that lets you run your batteries down to as low as 1.2V and still keep your Arduino alive. (But it is quite sensitive to over and reverse voltages - keep it below 5.5V!).