EmPower's technology allows one pair of lenses to be entirely normal focus and then, with the touch of a sensor in the glasses frame, switch to reading focus. The glasses, which do need to be charged overnight, look and feel no different than a standard pair of eyeglasses. We saw the technology in action, and the adjustment happens instantly.
Wearers can even set the change to happen automatically if they activate the tiny in-frame accelerometer (PixelOptic's reps say it's the World's smallest such sensor). With the sensor on, a tilt forward of the head to, say, look down to read something will activate the crystals and electronic focus technology.
I already read about this in MaximumPC but I'm sure tons of people haven't heard/read about it. Amazing stuff!