May be not a microprocessor. Building something like that requires moderately deep pockets.
But hardware start ups happen all the time. They don't have any where near the kind of press coverage we do. I am working on a couple of embedded projects on the side. And I can tell you the barrier to entry there is pretty high. Web companies for all their scalability problems are still by and large low hanging fruits, compared to any hard ware start up. There is also little VC activity there, and you won't get slots for pitches at conferences.
One of things that I see while working with embedded developers(I am currently working with some very good ones). C is literally the bread and butter, so you have no language wars. The highest priority is Stability(Read, Quality in general), followed by efficient code, and then maintainable code. Your survival largely depends on your ability to RTFM properly, you have to internalize and thoroughly understand specs, the hardware interfaces you are trying to program and the way C lets you program them in a interplay with best practices there.
Internet isn't always of much help as the platforms you are trying to target aren't too famous. And there are no hipsters who crazy blog every little development in that area.
Of the many things that I've learned(and enjoyed doing it), is to go to great extents to workout things on paper. Mind maps, diagrams, graphs, doodles, checklist etc. To first prove a degree of correctness on paper and begin to program. It has greatly increased my ability to divide things and look at them with clarity. In turn I am able to write stable, and quality code.
According to me every one should work a embedded project. Even if its not a serious project. And please work with plain C without an OS.
Additionally, writing a python program on linux, running on something like rasberry pi is not hardware hacking, or low level programming.