1) Most individuals here who want to monitor just 1 campaign don't have a strong brand. So there's very little value added with your app. They'll search for their brand on Twitter once a week to see the handful of mentions they get.
2) The BIG brand names already are using a platform like Hootsuite or SproutSocial to take care of everything social-media related. Which allows them to monitor their brand throughout the entire web(not just Twitter). As well as view analytics on their followers. And schedule messages.
IMO, your app is simply automates the process of searching for a brand name on Twitter. The categorization of the mentions into support questions, complaints, etc is not a huge value add, as most users will want to view all of their mentions, and don't care what bucket they fall under.