I'm not sure if the build really deserves a how to, but thought it might be interesting enough that some people may like it.
Some build notes.
The SMS is done using the Twilio API: http://www.twilio.com/
Weather data is obtained though the Weather Underground API: http://www.wunderground.com/weather/api/
Information on using both API was obtained through the Electric Imp website which showed a very easy and simple tutorial in using these API's: http://devwiki.electricimp.com/doku.php