Mask Pro 4 (current version is 4.1) is a tool for removing backgrounds to either show another background underneath or to be able to create a selection once the background is removed. Below is what Mask Pro 4.1 does:

Removes unwanted backgrounds with easy, intuitive techniques.
Maintains transparency in hard to mask objects like hair, smoke & glass.
Includes 12 tools to mask everything from large backgrounds to the finest details in hard to mask areas.
Works with 8-bit and 16-bit images in Photoshop CS2, CS3 and CS4.