Here's a quick thought: Android has a very nice, one-login solution for Google's services -- punch in your GMail password once and you instantly get push email, contacts, and calendar. Android is also fully open source -- anybody can download the SDK and take a look at the source code. That source code has to include some of the bits necessary to turn GMail from a pull service into a push service. Shouldn't it be possible to hack that code to make GMail push to Windows Mobile?
Now, it's possible that there's code on Google's servers that checks the device, but again, since Android is fully open source, it should be possible to trick those servers into thinking they're talking to an Android device.
Push GMail with full support for labels/folders has long been a holy grail for many of us -- Andriod's source code could be the way to get it.
What other Android-based benefits could we see on Windows Mobile?