Things I want to build:
An application to write books which have spaced repition engrained in their form. Most basic way I could think of is to give the writers options to embed thoughtful questions in their prose, and each reader would receive a mail at particular intervals quizzing him on those questions. Basically what Quantom country is doing.
An app built on principles of spaced repitition . I write down the things I want to remember as questions and answer them at intervals governed by practive of spaced repition