You know how when an idea pops into your head and you jot some random thoughts onto paper - sometimes notes sometimes diagrams, this app would provide a technological solution assisting in the gathering of several "brainstorms" into more structured ideas.
On a larger scope it can be used by groups (collaboration) of people in similar "brainstorming" or information gathering sessions.
One consequense though is that it would also have to support diagramming and modeling as in Visio or Rational Rose. This is beacuse many people in various disciplines (science and engineering espacially) use established diagramming styles/standards/syntax (UML, Flowcharts, etc.) when they are brainstorming.
I know some will view this as Apple once again taking away what should be left to third parties. I do not disagree but I will make a few points that I hope will show why Apple should proceed with this;
***looking at the targetted purpose that I have described, one can see that this is more than a diagramming app but the beginning of a potential future platform for intelligent apps. if eventually developed into a standard api this could be a boon for other apps - imagine brainstorming a musical composition by actually writing musical notes on a tablet pc
***this would be a boon for developers. i am still learning how to program and as a consequense i am learing UML as well. whenever an idea for an app comes to mind i usually scibble down a diagram representing the system.
***from the above examples, i am sure you have not missed that this (diagramming + note scribbling) would be one of those areas where you can actually get more done on a tablet pc. remember, developing an idea is a creative process an the more "freestyle" the capturing device/tool the more intuitive the creative process
***lets not forget that we a taking up microsoft so this tool (as described) is kinda a combination of MS Visio and MS OneNote (this is a pretty cool app)
***last and not least, this would be a killer app where groups are involved (collaboration, teamwork) AND it would fit nicely into academic environments