B & H actually lists both iPhone models in stock, while Amazon says they are temporarily out of stock.
B & H also lists Smoothee for the Flip, as well as different mounts (that let you switch between the iPhone and Flip) but there's no delivery date for those yet.
B & H: Steadicam Smoothee for iPhone 4 [$179.95]
B & H: Steadicam Smoothee for iPhone 3GS [$179.95]
B & H: Steadicam Flip Ultra Smoothee Mount [$24.95] - not yet shipping
This sample video was shot using the Smoothee:
Camera operator Michael Craigs is seen shooting with an iPhone 3Gs. The camera watching him shoot is an iPhone 4.