Flexible Linear Potentiometer

You can do linear position measuring by using this sensor. You can paste it on the surface that you want through to an adhesive backing. There is a nominal 10K resistance across the two outer leads. The middle pin resistance with respect to either of the outer pins changes depending on where on the strip one presses. When no pressure is applied, the middle pin floats, so be sure to use some sort of weak pullup, such as 100K ohm.