So far a few uses have seen the light of day, such as and even , but what of that most hot, hip, and with-it of social networks, Twitter?

A few Twitter iPhone apps have already started to integrate push notifications, though the implementations have varied. A few clients, such as , and have introduced push notifications for both direct messages and mentions (what Twitter formerly called "replies") into their existing programs.

While this is undoubtedly a better solution than adding push notifications for every Twitter update from your contacts--unless you enjoy exclusively using your iPhone as a device for dismissing pop-up dialog boxes--even managing mentions can still be overwhelming, as , for those with a large number of followers. Limiting notifications exclusively to direct messages, or providing more fine-grained controls over what triggers a push notification is preferable.

Twitter's direct message functionality, which lets you send a private message (as long as the recipient follows you), particularly benefits from the addition of notifications, since it's become a popular way for people to communicate, just like Facebook messages. In some cases, it's an excellent substitute for sending text messages, and push notifications helps bring it up to snuff with the iPhone's SMS support.

Several of the most prominent Twitter clients have yet to add any push notification support, however, such as , , and .