Image credit : UCLA

Invention turns cell phone into mobile medical lab - CNN, 2/3/09

This converted cell phone could take CD4 counts (used to monitor the progression of AIDS) or take red blood cell counts (used to diagnose malaria). I'm sure that the technology will improve rapidly.

The device reminds me of a miniature, mobile PCR thermocycler that was developed by some grad students ..

Real Time PCR on Disposable PDMS Chip with a Miniaturized Thermal Cycler - Biomedical Devices, Dec 2005

Since PCR amplification is one of the first steps in many diagnostic protocols (for diseases such as HIV and TB, prevalent in the developing world), a low-cost thermocycler could be useful for extended field work. However, I think energy would be an issue. I can't find a link right now, but I found a device last year that runs off of AA batteries. I'm skeptical of how precise these devices are.