That's a pretty awesome project. Instead of hacking the ARM, could you just call up a vet to ask if you can have some of their empty reagent bottles, and fill those with your homemade reagents? (As a bonus, if you can get it to work, the vet would probably be interested in knowing the reagent recipe as well.)

There's a movement towards open-source designs for relatively simple biological instrumentation- perhaps this sort of machine will be in range of those efforts someday soon.