MIT is on the verge of creating what could be the single most useful tool for optometrists around the world. By retrofitting a Nexus One with a microlens array or pin-hole array and then shooting beams of light into a person's eye, they can figure out whether you have myopia, hypermetropia or astigmatism and, if so, how bad it is.
The microlens array allows the phone to create a "4D interactive high-resolution light-field display" near your eye. This virtual display creates objects and places them at varying depths ranging from 1 cm to "beyond infinity". Basically, they've invented a vision test that doesn't rely on physical distance and can be administered (one presumes) anywhere at any time.
You can read more here. MIT will be putting out a press release tomorrow.
This technology has huge implications for patient eye-care, both here and in the third world. Those of us in wealthy nations can look forward to doing a pre-exam at home with our phone and shaving a few minutes off of our optometrist visit. Overworked doctors in poorer parts of the world will now have the option of doing more tests in a shorter period of time with extremely portable equipment.