The Song Fight Bulletin Board

So lots of you build apps. I'm helping my wife write up plans for a tablet app for speech therapy (that's her shtick). If you're willing and able to list the best case scenario for when someone sends you information to estimate (preliminary) effort and rates for app dev, I'd appreciate it. In other words, what are the most effective functional components of a app design that would allow you to make such an estimate? Once we write it up I'll send it to you to see about next steps (if you're interested in the work).