If you’ve got a jailbroken iPhone, you should definitely download biteSMS. It’s a free app in the Cydia store that basically puts the standard Apple SMS app on steroids. You can reply to messages without leaving the app you’re on, you can delay message sending (for those with terrible typos), you can set up scheduled SMS deliveries, and best of all, you can tell it to become your default SMS application (no redundancy on the iPhone).

Seriously, get your iPhone jailbroken and be a text message master with biteSMS.