There's an app for that.

If its as simple as spitting on a smartphone screen to see if someone has the flu, this is the most affordable doctor out there. Visionaries at KAIST (Korean Advanced Institution for Science and Technology) think that a smartphone screen might be capable enough to diagnose different types of disease from fluid body samples. This was inspired by the lab-on-a-chip design, which is a small device the size of a USB chip that is disposable and will be used for the detection of the disease.  A study was done to see if a smartphone screen was sensitive enough to detect different concentrations of certain liquid droplets at a small capacitance.  They took different concentrations of DNA from a bacteria that is known to cause chlamydia and used a smartphone sized multi-touch screen for a proof-of-concept test. Each droplet was only a microlitre and the screen's electrodes were able to detect the difference in concentration of the droplets.
This technology has not been created yet but is in the process of being created and this is why I was initially so interested in this article. After doing the nano-machine project I could see that so many potential things already around now could be used for biotechnology in the future. In our nano-machine the parts are around today but we predict that they will be smaller in the future so that they can be on the nano-scale these researchers are taking the multi-touch displays and predicting that they will be able to make an app that diagnoses diseases in the future. Their prediction might not be so far away in the future seeing from the studies they are already doing and hopefully this can be true for nano-machines ideas that we created.

http://www.newscientist.com/article/mg21228405.800-to-selfdiagnose-spit-on-an-iphone.html?DCMP=OTC-rss&nsref=online-news