The above link is referencing a new technology that is out for people who wear multifocals (bifocals, trifocals, or progressives). I was really excited when I first heard about these glasses. I like gadgets, and I like new stuff, and in theory this is a really cool idea. In theory these glasses act like distance-only glasses when you want and can be turned on to give you a reading power only when you need it.
I had the opportunity to try these out at Vision Expo last October. I wish I could say that they were everything I had hoped for, but there are some shortcomings. They do not really become a distance-only lens even when the reading part is turned off, there is just half of the reading power, so there is still some "swim". Also, when I was trying these out, I could not get the reading to turn on just by moving my finger along the temple. It took several tries, and I eventually had to get some help, which makes me think it would be a pain if I actually wanted the reading part on. The reading part has crystals in it, allowing the power to be changed, but they made the lens a little hazy, not completely translucent, with no wider reading area than current progressive lenses. Additionally, these are only available in certain frames, which are for averaged size faces - ok if you have an average-sized face.
All in all, I do still like the concept, but I think it needs some work. Maybe the second or third generation will be great. I'll keep you posted!