Cider doesn't really require all of the specifics of mashing temps etc etc, so I'm not sure it would be useful unless you are just trying to keep a record of the recipe there.
I use hopville.com for some recipes and they don't offer apple juice as an ingredient either. (Actually they do, but it only lets you specify in pounds not gallons) So it's kind of useless.
I am mostly trying to figure out an estimated OG after the fact. However, all of the calculators that i can find are for beer as opposed to cider. They all want to know how much malt i am adding.