Summary

A small device with a screen and some sort of input keypad, this thing would store a number of passwords/passphrases and other secret information encrypted with some sort of simple but proven cipher (such as a hardened form of RC4), and would need to be unlocked using the keypad before every use. Optionally, hardware could also implement a USB keyboard, auto-typing passwords for the user as necessary. Since it would be microcontroller-based and constructed manually and would have no network circuitry, the user could be reasonably sure that the password is essentially inaccessible except when actually in use.

Reasoning

Specification

Intelligence

Barriers

The usual suspects.