I would be happy to brain storm with you on your startup, but I'm not sure what kind of problems you are having. I've posted a bunch of personal insight into basic entrepreneurship on my blog, but I'd be happy to get more specific if you could share your situation.
It's unpaid, but also totally remote work so no relocating. It's a start-up company, but they've been around for three years so it's also an established team. If you're wanting to learn a lot about start up companies, it could be a great opportunity.
If you are serious about getting into a PhD program then you should have a clear idea of your academic/research goals and some professors you have impressed with your work. Compile professor recommendations, the write up of your goals, and any supporting evidence you have of your abilities: i.e. particularly noteworthy papers, projects, etc.
If you do end up getting rejected, then look around for a project with which to prove yourself. You know what skills you have and how they could be useful. Find another student's project, or a start-up company, or a professor's research which you can contribute to in an important and impressive way. You can use such proofs of your abilities as a ticket into a PhD program next year.
In the Health Care industry, when technology doesn't work the way it's supposed to people can die, or at least be seriously negatively effected.
Without at least the illusion of support from a big official distributor, that responsibility stays entirely on the shoulders of the person who selected the technology.
http://logic-shop.blogspot.com