Thanks to Benjamin Donnachie for alerting me to this nice bit of kit, a simple, relatively cheap weather station that you attach to your house and plug into the USB port of a PC. (There is an open source project to support this under Linux). The photos on this page should make it clearer how these things are physically attached.
Note in the US these parts are sold for $79. Not quite sure how they translated that into a £100+ price tag in the UK, but there you go.
“1-wire” is a semi-proprietary standard for sending power and low-bandwidth serial data over any two core cable (eg. telephone cable, speaker wire or Cat 5). The main advantages seem to be very long runs, and multiple devices can be connected to a single wire.
The device measures:
- wind speed
- wind direction
- temperature
- light level
Not rainfall — but there are 1-wire-compatible parts for making other measurements.
Richard WM Jones 
You may be interested in this – http://www.brain4home.eu/index.php?option=com_content&view=article&id=9:new-bae0910-multi-function-1-wire-slave-device-&catid=4:1-wire
Interesting piece of kit that offers the following over 1-wire:
Five I/O pins allows various functions:
• One to four 16 bits PWM: two hardware (PWM1 & 2) + two software(PWM3 & 4)
• One 8 bits ADC input 0 to 5V
• One 32 bits counter
• One strong (20mA) digital output
• One PIO, software selectable as INPUT or OUTPUT (20ma)
With the counter making an ideal replacement for the DS2423!