Portable Devices for Communications via PSK-31?

yipper asks: "Many amateur radio operators are exploring digital communication modes, one of which is a popular mode is called PSK-31. My local emergency communications volunteer group is thinking about using this mode for off-grid emergency setups. The problem is that a computer with a soundcard is more-or-less a requirement, hence my question: we need a lead on small, portable, battery (preferable 12 volt) powered systems which will run Linux or Windows, be easy on batteries, have audio in/out and a serial port. Recommendations can be older technology, as cost is a factor."