Niftech makes a spring dyno for motor and shock springs, here's a picture of theirs:
Here's what they say about it:
"Digital Motor And Suspension Spring Testing Fixture
Check back in the next few days to see the picture!
1. Measure spring force of electric motor springs and suspension springs digitally.
2. A totally new design of Niftech #4725 which incorporates suspension springs.
3. Works on laydown and standard motor springs.
4. Works on suspension springs for onroad or offroad up to 2 3/4'' long.
5. Precision machined by Niftech (Highest quality).
6. Comes with all necessary hardware (no hassles).
7. Easily comes apart for transportation to track.
8. Digital scale not included. Designed for use with Niftech digital scale #6010-NS-2000 (2000g) or for extra firm springs use #6010-NS-3000 (3000g). "
They get $150 for it, that's without the digital scale. As far as I can tell, it's only a spring rate measuring tool, not a true shock dyno.
Please keep us informed about your progress, I think a true shock dyno is something I'd definitely want to have.