Hello! I've actually tried to get a rudimentary translation service going to use for Mumble and couldn't get it working well enough, so I have pretty good familiarity with how we need to approach this project.
What sort of questions are you asking? One word answers only that can only have one answer? Any sort of ambiguity makes this incredibly hard. Showing a red thing and asking the color works, but even a mildly vague question would be problematic in getting answers, due to different users giving slightly differently worded answers.
I can easily setup so that we can send audio from Unity to Watson, read the results, and compare those results to the answer. If you can create questions that lack ambiguity, then I'm definitely able to finish this in a way you'll be happy with.
Thank you for your consideration as I look forward to working with you,
Adam