Elliptical is not an option at this time; however, a number of folks have asked for it in the past.
FitDay is in the process of a major revision, and one of the upcoming developments may include adding this. I also believe that being able to customize an activity (similar to making a custom food) will be an option as well.
IIRC from posts in the past, people have been using "ski machine" or something like that, which basically approximates a similar number of calories.
"If you drop an egg, you don't say, 'Oh, shoot' and drop the other 11, do you?"
-Source unknown, but obviously brilliant
Reached goal 4/16/2010...but kind of afraid to look these days