It also works from iPhone to iPhone – WiFiPhoto Review

I don't belive this is mentioned in the description, but I tried it with a friend and it works. Use the same method as if you were transfering to another computer. When the image shows up on the other iPhone's Safari browser, just hold you finger on the image for a couple of seconds and a menu to save the image pops-up. Great application that works well and does not require any special software other than the appliation itself.
Review by find my way on WiFiPhoto.