An article in Sensors (a magazine devoted to sensors and sensor technology) describes a new proposed standard for describing sensors and their data using a new XML dialect called SensorML.

The idea is to provide a standard language for describing the sensors and the kinds of data that they can sense, so that instruments can be created and joined together in an ad hoc fashion without regard to their manufacturer.

In the end, you will be able to build your own weather station, by hooking up thermal sensors from one company, barometers from others, hygrometers from others and anemometer from yet others and selecting each of them from software that comes from yet another supplier. Actual communication could be over IP (including wireless), or other technologies like serial and Bluetooth.