I'll be creating a lot of empty projects and place holders at first. I want to minimize the amount of throw away test code that is written, so I'll attempt to create each component is a way that will allow it to be used by other components during development and test phases.

I'll try hard to get at least a toe hold in as many areas that interact with each other as possible so that as in depth development is done in any one area, it won't seem like the developer is isolated from the rest of the project.

Integrate early and often so any incompatability in implementation or design is found and resolved as early as possible.

Having at least one thread through the entire application will allow the iPhone App developer control and monitor an actual sensor and will allow a sensor developer to control and monitor their sensor via their iPhone. (Why wait till the end to start having fun?)