It uses a simple interface to Dallas Semiconductor MicroLan Devices.
Temperature is measured by a 1820 digital thermometer.

You can find a description on how to build the interface and attach the sensor on my homepage.

myTemp supports the DS1820, DS18S20, DS1822 and probably the DS18B20 and DS1920.

You can attach as many sensors as you want to one MicroLan Bus.
here's also a demo, that runs without additional hardware.

Update Description:
v3.10:
- Support for OS5

v3a7 (6/19/01):
- Name changed to myTemp
- Timeout added for serial Interface to power on
- Logging-state is saved in the preferences between application starts
- Hardware Buttons work as expected (apply one button to myTemp in the Palm's Preferences)
- Bugfixes Multi-Sensor capabilities
- Added support for DS18S20, DS1822, DS18B20, DS1920 (the latter two are untested yet), besides the old DS1820