Dylan Schiemann has written about the role of HTTP streaming and Comet with respect to Android and mobile in general:

Given the critical necessity of low latency data transit with mobile devices, I wanted to find out what initial support is available for Comet on the gPhone platform.

XMPP is supported through the com.google.android.xmppService package. While the emulator currently seems to be hardcoded to @gmail.com domains, it looks like it will be quite straightforward to create chat applications for networks supporting the Jabber protocol. According to the documentation, to conserve network connection resources “the system currently maintains a single XMPP connection to the server, and all XMPP traffic — including both standard XMPP instant messages, and this P2P message-passing system — is carried on the same connection.”

The web browser included is WebKit, much like that found on the iPhone or Nokia’s S60 line of devices. In our initial tests using the emulator, the standard Cometd demos are not working correctly. We’ll be testing things in more detail in the next few days to try and determine if there are issues with Cometd, Dojo client code, or interaction with the emulator itself. We do know that most of the Lightstreamer demos work as expected on the emulator! One caveat: CPU consumption is substantial with the emulator and the Lightstreamer demo, though this could be related to animations or any number of other features besides the Comet data transit.

Given that this platform really does look like the same mobile WebKit, Comet server implementations that work on the iPhone should run on Android-based phones when they are released, with some work to do between now and then.
Between XMPP and WebKit, Android seems to give us significant options for both desktop and web-based low-latency data transit within mobile applications. If I have one complaint right now, it is that the SDK is heavily biased towards Java developers. I hope that changes prior to the final release, but for now it’s really nice having an official SDK well in advance.