I've been happy with a TempTrax unit. It connects via a serial port rather than PCI.
formatting link
You'll have to do a bit of hacking to read it directly from a shell script.
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer\'s. I hate spam.