Implement an API that gives access to this data on a per-user basis
We like this idea.
In fact, we're building an API for our own TwitSprout platform. We'll be using the API for our app - so you can be confident that it will be rock solid and well maintained :)
We haven't yet decided how to make the API available externally. Your input could certainly help guide our direction ;)
Feel free to connect via email / Twitter. We can learn more about exactly what you're looking for.