This is a great thought, but the mini-calendars in DayBack are really tied to the DayBack calendar interface. It would not be possible to grab just the mini-calendar and repurpose it for use on other layouts.
However, you might be interested in NinjaCal, which really does accomplish exactly what you are describing. More on NinjaCal at the link below. It doesn't look like Proof Group is offering NinjaCal for purchase directly on their site, but this page does have a link to contact them for more info.
http://proofgroup.com/ninjacalHope that helps,