title: Does Android support near real time push notification?
body: <p>I recently learned about the ability of iPhone apps to receive nearly instantaneous <s><a href="http://developer.apple.com/iphone/program/sdk/apns.html" rel="noreferrer">notifications to apps</a></s> <a href="https://developer.apple.com/notifications/" rel="noreferrer">notifications to apps</a>.</p>
  
  <p>This is provided in the form of push notifications, a bespoke protocol which keeps an always on data connection to the iPhone and messages binary packets to the app, which pops up alerts <em>incredibly</em> quickly, between 0.5 - 5 seconds from server app send to phone app response time. This is sent as data - rather than SMS - in very very small packets charged as part of the data plan not as incoming messages. </p>
  
  <p>I would like to know if, using Android, there is either a similar facility, or whether it's possible to implement something close to this using Android APIs. To clarify, I define similar as: </p>
  
  <ul>
  <li>Not an SMS message, but some data driven solution</li>
  <li>As real time as is possible</li>
  <li>Is scalable, i.e., as the server part of a mobile app, I could notify thousands of app instances in seconds</li>
  </ul>
  
  <p>I appreciate the app could be pull based, HTTP request/response style, but ideally I don't want to be polling that heavily just to check for notification; besides which it's like drip draining the data plan.</p>