These are things that serve a purpose but to my knowledge haven't been done yet.
- A collaborative learning platform, that would provide a place for notes, study tools, and interactive applications, that would make the whole process of going to class, taking notes and studying online and social. Etherpad is a good place to start, possibly Google wave.
- An encrypted messaging app that would act as an email and IM platform, but by using a system of keys, be inaccessible by any 3rd parties. Even if the data were stolen or turned over to governments, it would be unreadable. Search would be a big challenge, but there are some potential solutions. To make it transparent to the user, several keys need to be used, which provides several points of weakness.
- Asynchronous and concurrent programming is becoming more and more important. Instead of modeling calls with a stack, we can use a queue of functions to call and their arguments, and multiple threads can pick tasks from the queue and run them simultaneously. This makes debugging and exceptions hard.
- The computer keyboard has potential as a musical instrument. It would take a lot of design work and refining, and probably a long time to learn just like any other instrument.