Hi Matt,
I'm not aware of any tool or application that can provide overall search volume for a particular term on a daily basis. There are several ways you can half-extrapolate the data. You can find out a keywords share of search volume for a particular week (using a tool like Hitwise, for example) or you can set up an AdWords campaign, bid on the term and work it out from the impressions data provided.
However, I think you need to rethink why exactly you or your boss wants that data. SEO is a long term strategy. You can't just turn it off at the weekends if there is no search volume. If the aim is a to optimise a PPC campaign, however, you should be able to make use of the data Google provides.
Thanks,
K