I thought this was a pretty neat device that someone created. A grad student at TU developed a very compact device for testing people for pancreatitis. It's roughly the size of a quarter, and it is made out of some very surprising materials. The heart of the device consists of a very simple circuit board made up of a cathode and anode that lights an LED when the circuit is completed. On the circuit is a chamber formed from Jell-O which contains milk protein. The blood sample is placed in this chamber where the magic then happens. If the blood contains high enough levels of trypsin (elevated levels are characteristic of pancreatitis patients), it will eat through the Jell-O/protein mix. Sodium hydroxide solution is added which will subsequently eat through a layer of aluminum foil below the Jell-O chamber (only if the gelatin/protein has been dissolved by the trypsin). When the gelatin/protein and aluminum are no longer in the way, the anode and cathode interact with the salt ions to complete the circuit, lighting the LED. If the LED lights up in less than an hour, the patient has pancreatitis. I thought it was really cool how somebody combined their knowledge of physiology, electric engineering, and chemistry to make a cheap, convenient diagnostic tool.

http://www.popsci.com/science/article/2011-04/less-buck-sensor-made-jell-o-and-foil-detects-acute-pancreatitis-one-hour