This is pretty amazing! An attachment which can turn a regular iPhone (and eventually probably other smartphones) into a biosensor for inexpensive medical testing.
The project comes out of the University of Illinois and basically turns the iPhone into high resolution spectrophotometer. This can be potentially used to test for a range of things from the presence of pathogens and toxins, to allergens in foods, and possibly in the future vitamin A and D deficiency.
The great thing is that this is very inexpensive (around US$200 + the iPhone) compared to normal hardware used in laboratories (US$50,000), can be easily used in the field, and could bring these tests to areas and people who currently cannot access them.