Appremix has released a major update to its Boxcar notification management app for iOS devices. The new version represents a significant overhaul, sporting a completely new UI design and several new features. Boxcar 4.0 adds Retina Display support for the iPhone 4 and fourth-generation iPod touch, a and now provides a centralized inbox with more alert options. Several additional services are now available as well including Google Buzz, Google Voice and more and users can now reply to and retweet Twitter messages directly in Boxcar without having to open an external Twitter client. Boxcar is a universal app and is available from the App Store as a free download. The free version is ad-supported; users can pay $5 via in-app purchasing to disable the advertising.