As part of my thesis doing my BFA I wrote a program somewhat similar to this. It's simply a database program that one could create in Access (although I used FileMaker). My biggest problem was that I'm not a computer programmer and I had to learn the programming language on my own. My thesis was essentially a beta program with A LOT of bugs. That being said, if you're truly interested in creating a "virtual stage manager" you could do it yourself and customize it to fit each and every show.
After having done the programming, I realized that the types of shows where this would come in handy would be large pieces, with multiple rehearsal locations and various potential scheduling conflicts. I also hit a wall when it came to privacy concerns.
Upon a cursory inspection of the website (I'm not about to buy the program just to research it) it really is merely a scheduling database. That being said, I do feel there is a definite need for something like this and could potentially be an extremely useful tool. Please let us know how it works for you! Did you have to input your show information manually, or were you able to use one of their templates (i.e., a show already in their database)? How did the actors respond? Did they actually use the tools available, or did you still have to make the bajillion phone calls? Were you able to modify how much time to devote to certain scenes, or did it pick the times for you? How customizable was it? I've dropped my own database (haven't looked at it in 4+ years), but I'm still extremely interested in the technology.