I think a lot of that depends on how much time you have. If you're posting this FROM a hackathon, where presumably you need to get to work NOW, then some basic research online is probably the best you can accomplish.

- Is there a need for it? Are people asking for something like this publicly? - If you or someone on your team has a substantial social following, try kicking a quick question or survey out to the world and see what kind of responses you can get quickly.

If you have more time, then building a test page (even something as simple as a launchrock page) and seeing what kind of response you can generate would be a smart first move in validating. We did something similar to test a couple of our assumptions for our newly-launched product. We created a sign-up form that had 2 ways to sign up (allowed us to test one vs. the other) and then followed that with a one question survey that allowed users to respond as to which features seemed important to them.