The First Real Push Twitter Apps for iPhone: iTweetReply and Boxcar

[wraggster]

iTwitter had push notifications for mentions and direct messages, but only from other iTwitter users. iTweetReply supposedly works for any mentions or DMs. Not the prettiest or most feature-packed, it's $2 if you're dying for Twitter push.

http://gizmodo.com/5311986/itweetreply-the-first-real-push-twitter-app-for-iphone