So attempting the serial (USB) connection between the Arduino Uno and Raspberry Pi and then sending the FSR data from one to the other. I'm using a Raspberry Pi 3 Model B, this model has the most connections, everything you need in terms of HDMI output/USB ports to make this stage of the prototyping quick and easy. 

So here, I have a keyboard and mouse connected to the two USB ports on the right. The power cable of the Arduino Uno is then connected into the lower USB on the right. Then you can see the HDMI cable outputting to a TV I have connected and the Raspberry Pi power cable at the rear. 

After a google search on the serial connection and reading/writing to it from the perspectives of the Raspberry Pi and Arduino respectively it seemed fairly simple. 

This stage, I used essentially the code available here for the basis: 

https://classes.engineering.wustl.edu/ese205/core/index.php?title=Serial_Communication_between_Raspberry_Pi_%26_Arduino

So I wrote up a quick serial test python file. First I just want to get the data to the Pi itself, I will then move onto getting it into the Kivy GUI. I will upload this serial test file and the Arduino serial code file for that side of it too.