I was reading up on iPhone in the enterprise and saw something about Mobile Device Management servers. As far as I can tell, there are a few 3rd party MDM vendors, but Apple says that one could implement their own.
The iPhone Configuration Utility allows you to set up a Server URL, Check in URL, Topic, Identity, and some other things for an MDM, but there's little information on how to build a server that hooks in with these.
I've looked in the Enterprise Deployment, iPhone Configuration, and even the iPhone Mobile Device Management docs, but have found little aside from vague mentions or the occasional diagram. Is there a documented protocol somewhere?