As an observer to the startup scene, one pattern that puzzles me is the habit of jumping onto technology trends (currently cloud mobile/smartphone). The economics of consumer electronics mean that processing per watt continues to drop which means that increasing amounts of functionality previously tied to your PC becomes untethered. Combined with cloud infrastructure, this means your digital personae travels with you (as indicated by red space).

But what are the constraints ... power density, screen diameter, and network latency. As a thought experience, let's consider what radical innovations may bring

2. low power = disposeable phones, high power-density = multi-week devices. 
3. small aperture = watch-sized devices - micro-projectors

And given the price sensitivity of consumer electronics (not an economic durable) what are the potential applications?  The point of this introspection is not to give sloutions. In science, often the question is more important than the answer. Imagineering is a systematic process of imagination + engineering, looking through the dimensions of possibilities and considering what product lines fit the blue line. The impact can be seen in the japanese desktop copiers undermining of Xerox. In the old days, the metric was cost per page in a leased machine. But by suddently providing a cheap fax-like device on the desk with a toner-cartridge business model, they created an entirely new category.

Let your imagineering be your entrepreneurial guide.