This LilyPad Simple board is controlled by an ATmega328 with the Arduino bootloader. It has fewer pins than the LilyPad Arduino Main board, a built in power supply socket and an On/Off switch. Any LiPo battery can be plugged right into the socket. The Simple board is designed to give you more room to work and eliminating the need to sew a power supply.
LilyPad is a wearable e-textile technology developed by Leah Buechley and cooperatively designed by Leah and SparkFun. Each LilyPad was creatively designed to have large connecting pads to allow them to be sewn into clothing. Various input, output, power, and sensor boards are available. They're even washable!