@terran - I went through search results from google, and can't find it. I see plenty of information on Fidelity's workplace HSA ("fidelity hsa"), but searches like "fidelity individual HSA" haven't shown me details, like fees. How did you learn about it, and can you share what page or search you used to discover details?
Pending that information, I've been using HSA Bank. While their fees are higher than other HSAs, they allow a $0 cash balance and 100% investment. Compared to my prior HSA which required a minimum cash balance, the higher fees are offset by allowing more HSA money to be invested. HSA bank has an arrangement with TD Ameritrade, so trading costs are $7/trade for the investment portion.
But I would hold off on HSA Bank until you learn details of Fidelity's individual HSA - it sounds like an improvement.