This is a great idea, so I did a little digging to help you on your way.
I love the idea of having a home weather kit, since it sends wireless information, I guess you only need to pick up the information on your computer (as the monitor device would) and relay it out to Pd. You'd need to reverse engineer this as in my searching, I couldn't find anyone who already has. There are various ways to get data into Pd. create a script using any of the languages that your (Mac OS X) Terminal can interpret b(BASH, PHP, e.t.c.) . I think you have to write it to send messages to the 'Standard Output' or stdio or something, which you can then call from within pd using the object [shell]. OR... Write your program in C and then package it as an external for Pd. OR... Find something that can parse the data and send it forth using the OSC (Open Sound Control) protocol. Pd has objects that can utilize OSC.
So lets say we want to take our feed from weather.com or from one of the sites, we have to parse the information in PHP. This claims to do such, but many people complain it doesn't: http://53x11.com/blog/2005/04/15/Weathercom-XML-Parser-14.5 You would have to modify the above script, to, instead of writing out a file, to broadcast the information over OSC. There is an OSC class for PHP here: http://andy.schmeder.net/software/
Since the weather parser doesn't actually work, and weather.com only permits you to request data once every few minutes, you may find better luck on some of the other weather engines. Maybe yahoo has something for you to parse.
But then, after copious amounts of a head scratching and research, and some wisdom points later. You will have done it! (Plus learnt how to do some very basic PHP tweaking. which is cool).
Of course, meteorologist is open source, so you COULD tweak that to broadcast OSC, or ask/bounty the developer, but you won't have learnt anything along the way.
I hope this gets you started.
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