Hi All,
I recently completed a project which interfaces the RPi with a load cell. It measures how strong you can squeeze the load cell and plots your grip strength on the screen.
The entire project is up on GitHub: https://github.com/michaelorr92/grip-strength
There you can find the code to interface the load cell; how to download and compile it; and some hardware files so you can manufacture a PCB easily.
The code should work with any load cell than can run from the RPi (i.e. can run on 5V).