I have also been alerted to these.
They have 4 prongs inserted in a bubble of fluid. as the fluid moves ot changes the capacitance.
They are only 5 bucks too.
http://www.goldmine-elec-products.com/prodinfo.asp?number=G15429&variation=&aitem=8&mitem=12
Dual axis electrolytic tilt sensor type SP5010-A-006 is similar to the SP5000 shown on the Spectron Website (
http://www.spectronsensors.com).
The sensor features 5 PC board pins and a special liquid electrolyte housed in a .433" diamter x .865" glass cylinder. The electrolyte used in these sensors is an alcohol based fluid, contains no heavy metalss, and is non-corrosive. These sensors are used in oceanographic, aerospace, medical, GPS, etc., applications. There is a circuit on the WEB of an RC helicopter which uses one of these to provide information on tilt as it is flying. These sensors are very unique and are hard to find on the surplus market. Brand new - no data supplied. Has factory label SP5010-A-006. Check out our incredible price! G15429