So you want to build your own smart wearables? The MyoWare Muscle Sensor Development Kit has you covered. It is an Arduino-powered EMG sensor with everything you need to measure electrical activity of a muscle. MyoWare lets you control robots, prosthetics, and more. With 3-pin stackable headers, connecting components is easy.
The kit comes with a Muscle sensor, power/LED/Proto shields, biomedical sensor pads, and other components you need to get started. As you can see in the above video, you can use these sensors to light up LED lights while flexing your muscles.