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Address Book

The address book via bluetooth connection to the phone (I use a t68i). When you have the bluetooth hardware in place restart Address Book and a little Bluetooth button will apear in the top left of the interface. Click this (and all going well it will turn blue). Now click on the label that says Mobile : and you will see an option to send SMS.
 
Also, in iChat you can use the AIM SMS service. You do this by adding your phone number as a buddy in the form of +15558089921 ie you type the + sign, the 1, area code, and phone number, without dashes or any punctuation other than the starting +. You do this by clicking the plus at the bottom of the Buddy list, then clicking "New Person". You can add address book information if you desire, but if you don't, it won't create a separate heading for the "Mobile" buddy. When you IM the phone number, it gives you an automatic response saying how it's a one way communication and the person can't respond from their phone.
 
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