How can I remotely send an SMS message through my Mac from my iPhone?

You can use myPhoneDesktop.

This solution has an iPhone and Mac (or Windows) client and sends a push notification from the Mac app to the iPhone with the information for a call, text, URL, text or an image. The iPhone app then opens the data sent to it by the Mac app.

The iPhone app costs $4.99 in the App Store and the Mac app is free. myPhoneDesktop requires an account to be set up, but it is free.

Apple has actually just released this app which should do just that. It works only with ios5 and mac os10.7.3. Its called messages. It is a beta version of an app that will be on mountain lion.

I downloaded it from http://www.apple.com/macosx/mountain-lion/messages-beta/

Depending on your use case, you could send SMS messages using Google Voice for free. Google allows you to port your mobile telephone number for a fee if keeping the same number is important. You would then be able to send SMS messages directly from your desktop, or anywhere else you have an internet connection and web browser.

If applicable, could you explain why you'd like to send the SMS through your iPhone instead of directly to the recipient?