I don't care much for setters in a case like this. I'd prefer a method, but don't feel strongly.

Jim's suggestion of using the word "enable" is better than "set", though. So if it was me, I think I'd use a method named enableNFC() or enableNFCSharing().  I don't think underscores are necessary here, either, since this is not a library that other app are going to be using.  But again, I don't feel strongly about that.