I have worked on medical projects, and here's what I know. With medical, the medical related certification you need (in the US) is what's called a 510K pre-market approval from the FDA. Now, you only need the 510K if you are going to market and sell it. If you aren't doing that, then you don't need 510K approval. Part of the thinking is that experimental research devices (usually overseen by a MD) can be tested without going through lengthy review. Of course once you have the intention of marketing and selling, you would want to start filing for it. The FDA did put in new ruling for mobile apps recently though, basically it's an exemption for 510K for that category.