Thanks for putting your blog together and sharing your source/diagrams. Your weather station is very polished, at first glance I thought it was a commercial item until I saw the photo of the build on your workbench. I take my hat off to you, you have put in a lot of effort and it shows. Well done.

I emailed BlueVia last week regarding availability in Australia for their new Arduino GSM shield, the reply I received indicated that it was only available in certain international locations: http://bluevia.com/en/page/tech.arduino.service and when it becomes available the shield can be purchased through the Arduino Store.

I was given no indication of eta but I was told that using a SIM card other than the one supplied from BlueVia would not be supported.

Hey Dolf,
  I too am an Arduino newbie and would like to produce a similar Google Latitude GPS tracker and started looking into it a couple of months ago. I have not developed anything due to other commitments but will try and pass on what I found.

Jayesh has a good tutorial on Blogspot http://jayeshprojects.blogspot.com/2010/04/real-time-mobile-gps-tracker-with.html for a Arduino GPS Tracker using Google Maps and a GPRS module, he uses Application and a SQL server as opposed to sending the information direct to Google Latitude.

From what I've read Google Latitude can only receive information in the form of java script, to overcome this Ben also posting on Blogspot http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1286813442 communicates from Arduino directly to the Google App engine then to wherever you wish.

Other stuff;
http://tronixstuff.wordpress.com/2011/01/19/tutorial-arduino-and-gsm-cellular-part-one/ a GSM Arduino tutorial
http://tronixstuff.wordpress.com/2010/09/17/moving-forward-with-arduino-%E2%80%93-chapter-17-%E2%80%93-gps/ a GPS Arduino tutorial

Have fun coding,
Brad