i don't know whether you can extend your existing visa but this should be on the top of your list, also make sure that you find permanent solution for the status for living in USA (or north america)... trust me, H1B or any other temporary visa is not a permanent solution, you're always worried about loosing your status and have to go back to your home country. One small change in immigration law can put your hard work in jeopardy.

i know many who apply for Canadian permanent residency (same as USA green card) so that they atleast have stability and dont have to go back and forth to/from home country. Canadian PR is easy and fast and you can work from Vancouver (closet to silicon valley on canadian side) and in the mean time keep working on your project and on some kind of visa status in USA.

edit: also once you've PR from Canada, you can go to US on visitors visa as many time as you want, this is good if you want to meet VCs or other project related partners/members. Also you can get Canadian citizenship within 3 to 5yrs after PR.

Do I sound like sales guy for canadian immigration :-) anyway find a lawyer who has knowledge of both countries (USA & Canada), again trust me this will immensely helpful for planning your future and stability.