For customizations you must jailbreak
I've seen a lot of threads where people are asking about certain things to customize iPhone native apps and/or settings. Here's the thing about the iPhone that's been known for the last 3+ years, it's not very customizable. You can't do anything to the native apps and other apps are only customizable as much as the developer makes them. So...... if you want to be able to add a notification bar, change the SMS app and how it looks, themes, etc you must JAILBREAK.
I know there is a lot of apprehensiveness with jailbreak for some. But the process is completely and easily reversible so don't worry about "voiding your warranty". A quick backup and restore erases the jailbreak. So what I would suggest is try jailbreaking and open the iPhone up to more app, tweaks and customization options. Visit the jailbreaking forum for more info. Hope this helps.