Its simple to get biteSMS app for free. biteSMS is cracked by SiNfuL iPhone.
Imagine you're browsing the Internet and an SMS comes in. With Quick Reply there's no need to quit Safari, just reply straight away, or leave it and deal with it later from the Quick List.
Works in any app, not just Safari. The color of the Send button shows you how you'll be sending it: pink via biteSMS and blue via Carrier. You can switch by holding down the Send button for a few seconds.
Quick Reply works in landscape too:
And, it works in the lock screen too!
On the lock screen, the pink biteSMS icon is added when a summary appears: