This is a simple 8-inch long 2.5mm audio cable. It is terminated with a three-pole 2.5mm plug on one side and unterminated with bare wires on the other end. These are intended to be used with the ModKit MotoProto Shield — solder the wire ends to sensors.
You can use this to experiment with anything that uses three-pole 2.5mm audio jacks. Note however that this is not the standard 3.5mm (1/8-inch) size used for most headphones or line-in/out stereo jacks. The plug on this cable is the smaller, less common 2.5mm size used on some cell phones, cameras, and other portable electronics.