I got it working with a pull up (tried pull down too) resistor, and it connected to an analog pin. I can read the it just fine, the problem is just that when I don't touch it, it reads 0 like it should. But as soon as I just touch it a little, it jumps up to 4-500, and adding a little pressure more it goes up to 800. After that I need to press a lot harder to make it go up, and with around 1 kg pressure on it, it is at ~950, 1.5 kg ~960.
From the curve graph (figure 2) is seems not linear at the low force end. The datasheet goes on to tell of various ways to correct or improve on linearity/accuracy.
It seems to both rely on area and force. I tested with both just pressing with a finger, and with a dvd between to make sure it was spread more out, and both gave very close to the same result.
I haven't really planned anything yet, I only got them because I ordered another arduino and saw they were cheap on the website. So just playing around with them for now.