As it turns out, prayers do get answered. Although Iconfactory gave Twitter on the iPhone a try, MobileTwitter is currently one of the only known native Twitter application for jailbroken iPhones. The application allows you to tweet, follow your friends, and manage direct messages right from your iPhone without using up precious SMS messages.
Before this app, I was personally using the oh so beautiful PocketTweets, but that got painful over EDGE. The app doesn't currently run in the background, although I'm not sure the developer intends to allow it to do so. To update your twitter feed, you simply open the app. And not only can you post a tweet, you can also take photos from your camera and post them to twitpic.
MobileTwitter is available from Installer.app under "Network". Although it's still a little rough, this app has made it to the first page of my iPhone's apps.