I purchased a Clinometer to measure the tilt angle of something. Thought I'd post some details for anyone looking for something similar.
Part number 824-02110002, MSI Sensors, Clinometer, Single Axis, Vertical mount. Price of $137 plus shipping.
This particular sensor is good to 60 degrees either side of center. It has no moving parts, but does contain a fluid which is what is used to determine angle. Unfortunately, that also causes a "slosh" effect while bouncing, so I did have to add some averaging to get it to move smoothly.
This sensor is ratiometric, so you give it 5 volts, and it will output 2.5 volts when level. Output voltage goes up or down based on which way it is tilted.
Mouser Electronics Part
Data Sheet