Drew Fustini tweeted about a presentation he saw at LinuxCon 2014

A Teensy 3.1 was used for a DIY security token.  The functions inlude Trusted Platform Module (TPM) for Integrity Measurement Architecture (IMA) attestation, signing files, and ssh remote login.  Some of the features include private keys generated on the token and a physical presence required to reprogram.

The token was simply constructed using the housing from a USB thumb drive and some epoxy to keep it all together.