Our mobile devices have various apps that need updates from various servers at various intervals. Each app connecting to its own server on its own schedule, perhaps using inefficient technologies, can cause a lot of battery drain. Push Notification services are systems that can route all the important updates our devices need - whether they're instant message, VoIP, or social updates - into one shared channel.
Unfortunately, the status quo in push notification services rely on centralized, proprietary services hosted by a third party. UnifiedPush is a set of free and open source specifications that allow you to get push notifications while picking your own hosting provider. This presentation goes over the history of UnifiedPush, current state of the project and architecture, and what the future goals of UnifiedPush are. It also discusses push notifications on Linux phones.