Those things are great for us guitarists.
First you would need to fit some sort of sensor to each of the finger actuators which measure their mechanical movement. Then you'll need to tie these sensors into a microcontroller, and firmware will need to be written to measure the output of each sensor and convert this output into distance of movement.
You would also need to measure how many lbs of force is required to move each actuator a given distance, then code this information into the firmware. This information along with the distance of movement will be used to output the lbs of force applied to a display unit of some sort.