Happy Valentine's Day!
It's an Open Source heart rate monitor created by Sensebridge, a group of smart hackerspace folks from Noisebridge in SF and hacklab.to in Toronto. The device is powered by the ATMega168 and the source code was developed in the familiar Arduino IDE. Users can download the Arduino source code from GitHub & reprogram the device via a header on the back for a FTDI cable. The optional epoxy finish on the front looks great in person but limits future hardware expansion.
The lead designer Eric Boyd has followed up the original version with a new beta version which logs to an onboard EEPROM. The data can then be uploaded to a computer for analysis and graphing. Since the Heart Spark project is Open Source Hardware, anyone can download the EAGLE schematic & board layout file and dream up there own version.
I ordered a Heart Spark and the recommended Polar Wearlink Transmitter with Chest Strap last month. It's works fantastic, and my girlfriend loved it!
BTW, while you're on the Sensebridge website, be sure to check another amazing project from them: the North Paw. It's a "an anklet that tells the wearer which way is North."