The Oculus Rift is a great piece of equipment, and up until now you needed to use motion--based controllers to simulate your own arms in some Rift games. Myo looks to take things one step further by freeing up your hands, thus creating a more immersive experience.
The way the Myo works is by detecting the electrical activity in your muscles in order to tell what kind of gestures you're making with your hands. The device uses Bluetooth 4.0 low energy connection, proprietary muscle activity sensors, ARM processor, a 9-axis inertial measurement unit, and a rechargeable Lithium ion batter. Plus there's haptic feedback.
Myo is available in both black and white for $149, but note that's just for a single unit. Dev kits are on offer at the same price too.
Great way to suck players into the world of virtual reality better, but it's going to be a bit too pricey to get the full immersive experience for both arms. It's a good start though, at least. What we really need are gloves that can be connected to the Rift for individual finger action.