The plug rage continues … this is a plug to measure temperature with either a thermocouple or an NTC resistor:
The chip is one of the AD594 .. AD597 series for use with J / K type thermocouples. With an NTC, the chip and 2 caps should be omitted, with a pull-up resistor added instead.
The other I/O pin is used for a piezo buzzer. It is driven via an NPN transistor with the positive lead connected to PWR to increase the volume. An alternate use for this pin + transistor is to control a relay or an opto-isolated triac.
Depending on the parts used, this might make a nice plug for a JeeNode-powered reflow controller. Or a temperature-controlled aquarium / soldering iron / 3D extruder / whatever. Or up to four overheating sensors, when used with multiple ports.