I've talked with the DV Rack folks..you will have to buy a PEECEE to use it....they say the Mac Version isn't in the works because:
(from their Web site FAQ)
Is there a Mac version of DV Rack?
Unfortunately not, DV Rack makes extensive use of Microsoft?s DirectShow technology which is only available on Windows itself at this time. Serious Magic does not currently expect to be able to port DV Rack to the Mac platform. Fortunately, laptop PCs are quite inexpensive and DV Rack is designed to work in a multi-platform environment. It supports writing files that are compatible with popular Mac software such as Final Cut Pro, Avid and Media 100.
The Company - Serious Magic - makes an excellent virtual background/keying program...but alas...no Mac products...because:
(FROM THEIR FAQ)
ULTRA relies on Microsoft's DirectX architecture to generate high-speed output from PC graphics cards. Microsoft does not offer this architecture on the Mac at this time, and there is no word on when or if they will. However, ULTRA does read Quicktime clips and can exchange clips and stills seamlessly over a network with Macintosh based production systems such as Final Cut Pro.
BUMMER - Andy