Remember the MyoWare powered Iron Man Glove that we covered recently? The MyoWare happens to be a muscle sensor platform that can be used to control robots, prosthetics, and video games. It measures muscle activity through the electric potential of the muscle (EMG) and generates an analog signal representative of how hard the muscle is being flexed. You can connect your MyoWare to 3.3V through 5V development boards.
It offers an output of the RAW EMG waveform and has LED indicators to let you know when it is on. There is also an on/off switch. The MyoWare is Arduino compatible. It can be used to create bionic claws/gloves, control robots, and play games. You can find out more about it on Kickstarter.