Device costs less than $5 and can accurately measure the number and speed of swimmers. Source: With racy sperm pics on a smartphone, men can easily test fertility | Ars Technica If  only Theranos could do as well!

This is just a research project. But it’s still impressive. Smartphones have elaborate sensors, computation, networking, and even databases. Adding a custom sensor modifier will bring lots of inexpensive tests, medical and otherwise.