The title says it all, you can send and receive SMS text messages through iChat by following these simple instructions. If you are so inclined, there is even a simple bash script allowing you to interface with iChat through the command line for such purposes. This is a great tip found in the MacOSXHints archives, apparenty the ability to send SMS messages through the AIM protocol has been around a while (note the date on their article is from 2003!).

• Hit Command-Shift-N to bring up a New Chat window
• Enter in the phone number you wish to text message in the following format: +18005551212
• +1 is the country code for the USA, so if you want to try other countries, change it accordingly. +44 for the UK, +49 for Germany, etc
• Note: I have only tested this in the USA, so no guarantees with other countries
• Type your message and click send
• Now you can talk with any mobile phone through IM and Text Messaging

As you can see from the below screenshots, you will get often a message confirming that the instant message was sent to a mobile carrier. Because it is AIM that allows for this, technically this tip should work for Adium and other AIM supporting protocols as well, but I haven’t tested them.

You can also send IM’s through iChat via the command line with this simple bash script (found in the comments on MacOSXHints, credit to their user ‘below’):
#!/bin/sh
# I got my wisdom from http://rsvp.atsites.de/stories/storyReader$194
# Apparently, iChat wants it that way
osascript< tell application "iChat"
repeat with a in (every account where id is "AIM:$1")
send "$2" to a
end repeat
end tell
DONE


Simply paste that into a text file with nano, save it as sendsms.sh, chmod +x sendsms.sh, and type ./sendsms +18185551212 “hello”

Note that the above bash script still requires iChat to be open, and still sends the SMS through iChat, allowing the conversation to continue in a typical iChat window.

Source: MacOSXHints