A simple flex sensor 4.5" in length. As the sensor is flexed, the resistance across the sensor increases. Patented technology by Spectra Symbol - they claim these sensors were used in the original Nintendo Power Glove. I love the Nintendo Power Glove. It's so bad!
The resistance of the flex sensor changes when the metal pads are on the outside of the bend (text on inside of bend).
Connector is 0.1" spaced and bread board friendly. Check datasheet for full specifications.