Requires iOS 4.2 or higher
SMS+ is the best solution to improve your SMS experience on iOS. It integrates perfectly in the native SMS application, adding to it those functionalities you won't ever be able to stay without after having tried them.
SMS+ allows you to quickly reply to an incoming sms without leaving the app you're using, or even bring up (via an Activator gesture) a new window where you can compose a new message, choosing the address from your contacts. It also includes a "Later" feature, which you can use to keep a message unread to read it later (an icon in the Status Bar will remember you that it's there). You can also choose to make your iPhone "speak" an incoming message, maybe when you're driving or you can't look at your iPhone's screen. There are also some other extra options right inside the SMS app, like mark all messages as read, delete all messages, timestamp every message, show/hide conversations and a "Pull to sort" feature, to toggle the conversations sorting between dates and senders.
SMS+ actually improves your SMS experience!
No new icons will be added to your homescreen. Configure SMS+ options from your Settings.app
See all the Screenshots below