A new web mentions tool from SEOMoz, still in beta, appears to provide web mentions data that accurately matches keyword-based traffic your site will receive.
What we are seeing is that the direction and magnitude of changes in web mentions, by keyword term, appear to match actual traffic charts we’re seeing for production sites that feature those terms.
In the diagram above, we asked for SEOMoz to show us 2 weeks of data for virtual call center and toll free numbers. The results are very close to what we see in production for some of our outstanding customer sites that we track, such as www.avoxi.com and www.callforwarding.com.
This means that day-to-day ups and downs shown in the SEOMoz Fresh Web Explorer will reflect the same traffic in your site, if your site uses and features those terms.
Going further (speculating), it may turn out that you can use this tool during keyword research, in a way similar to using Google Insights for Search, only with more immediate data – the last two weeks, not all the way back to 1999.
This is certainly worth checking, would like to hear your comments and experience with other sites.