Smash the phone? That's terrible advice. For just about everybody, destroying the phone is probably going to get them in a lot more trouble than the contents ever would.

If you don't cooperate they can hold you for a while and make all kinds of threats but, if you are a citizen, ultimately they cannot deny you entry.

If I were truly paranoid, I'd probably travel with flip phone and an iPad with typical (non-sensitive) apps on it and a remote desktop client that I could use to connect to my computer back home. Make sure the remote desktop client isn't installed on the iPad during border crossings.