Mimicking Google Account on the server-side

Question

I recently bought an Android device. Now I'm wondering if can I mimic protocols it uses to communicate with Google servers? I basically want to setup some kind of "Google account", which wouldn't be served by Google, but would be fully compatible with Android devices. So, does Android use some kind of WebDAV protocol for accessing things like calendar, contacts? What kind of protocol does it use for mail (is it IMAP, as I would configure my account on a PC or some other Google-only-knows-what-is-it protocol?) Or do I just have to mimic GData protocols? Is there even a way to change host which Android talks to?

I know that there are things like Google Apps. They allow you to setup your own, very little part of Google, which AFAIK can be connected to Android device (you just have to create an Google account with your domain after username, I suppose), but everything's still hosted on Google servers and Android still talks to Google host.

If nothing works out, I could probably create some kind of service provider, which would act like those for Facebook, Twitter and Google, but for now I want to explore possibility of doing it on the server-side.

Not that I don't trust Google. I just don't really like someone handling valuable part of my life in files I don't own. Assume this question void if someone found a way of chowning files on Google servers ;).