Getting glasses can be expensive. First you need to see an eye doctor to get your vision tested, and then you have to pay for expensive custom ground lenses and frames. These glasses simplify that process, by letting you adjust the correction manually to get the sharpest view.
The glasses use two lenses that slide across each other changing the power, using a simple thumb wheel on each temple. You just turn the wheels one eye at a time until your view is the sharpest, just like when the optometrist tries out different lenses during an eye exam.
One big plus is that you can adjust the focus depending on the situation, so you won't need to carry around separate distance and reading glasses. They kind of remind me of those electronically switchable glasses I saw at CES last year, but at $40 a pair they're about $1160 less than those fancy versions.
The low price of the Eyejusters makes them perfect for people in developing countries, where getting custom made glasses and a trip to an opthamologist simply isn't an option. They may look kind of goofy, but that probably won't bother you too much if the choice is between seeing clearly and barely seeing at all.