Search warrants can compel you to give police access to your property, which can include your body (in cases of blood draw warrants in the case of DWI). The police can obtain a search warrant for your physical filing cabinet, which includes taking measures to access it if you won't unlock it for them.

Police can easily get warrants for your phone; you just can't be compelled to give the code to unlock. I suspect in the future we'll see a different level of cooperation from phone makers.