Good luck with that. If you are on a 'real' OS like Linux or BSD and have *coins there, I doubt anyone would know. Especially if you have disk encryption and using a trusted VPN or tor or something like that. Remember to enable MAC spoofing too.

If you have your wallet on a Cell Phone, you might as well post a sign outside of your house stating "I am a bitcoin user and trying to keep that use secret" :)