They are force sensing resistors, arranged in a crossbar matrix. The resistance is roughly inversely proportional to pressure. Look at the Parallax product, and app notes, http://parallax.com/product/30056. On the Prop, you could do something with rctime or a sigma-delta adc. I don't know specifically about the shoe. You'd have to dig into it or find more info. Possibly they have an interface of some sort built in. Does it do bluetooth?!
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https://www.tekscan.com/product-group/medical/in-shoe
I'm just Intrested in the readings for a robot foot to help balance