From Alco Blom Software:
How do you send an SMS? Are you using the T9 input method? Are you also wondering why you are using these small keys with numbers on it to enter text while you have your Mac keyboard in front of you? Then the Send SMS widget is for you. Use your Mac to enter SMS text and then send the SMS through the Internet. You don not even need a mobile phone. The widget will send the SMS for you.
Each SMS will cost you only 10 cents, whether you are sending locally or to a foreign country. No roaming costs are involved. In the USA and Canada, you can send SMS for free if you use our new email2SMS feature.
Unicode, Long SMS, Caller ID and delivery reports are supported.