Those of you looking to be able to send your text messages from the computer, rather than your iPhone, should check out a jailbreak tweak in Cydia called Remote Messages
by iOS developer Beast Soft
On Mac OS X Mountain Lion, users can take advantage of the native Messages application to send their iOS-using and Mac OS X Mountain Lion-using friends iMessages, however it doesn’t go as far as to support SMS. This is where Remote Messages comes in. Remote Messages also works on Windows, and other platforms where Messages for Mac is not applicable.
As shown above, Remote Messages will keep your text messages in sync