Evidence is not covered by the Fifth Amendment. If you have papers that would incriminate you, and a warrant is issued for those papers, you cannot refuse to surrender them. If you destroy them having received the warrant, you'll be prosecuted for obstructing justice.

Orin Kerr's interpretation[1] is that a phone is evidence, and contains evidence in the form of digital data. The only need for testimony is to establish that the phone is actually yours. You can't be forced to admit "yes that is my phone." But if the fact that it is your phone can be established in other ways (say, with the testimony of your wireless provider), then you can be forced to unlock it.

You can't be beaten or tortured until you type it in, of course, at least within the U.S. But you can be jailed for contempt of court for your refusal. And the limits of contempt imprisonment seem to be pretty murky.

[1] http://www.washingtonpost.com/news/volokh-conspiracy/wp/2014...

Edit: to clarify the source of my argument

You don't need a finger to circumvent touchid. You can just obtain your victim's fingerprint from anywhere (e.g. a glass that they used) and create a fake "finger" using household items:

http://www.ccc.de/en/updates/2013/ccc-breaks-apple-touchid