Microsoft just opened a new beta program for the Hyper-v Management Pack for System Center Operation Manager (SCOM) 2007 R2.
The management pack is incomplete for now as it only allows to monitor the health of Hyper-V hosts that are part of Windows Server 2008 full (Standard / Enterprise / Datacenter).
No support at the moment for Windows Server 2008 Core Server versions or for the stand-alone Hyper-V Server 2008.
The program is not directly available on the Connect website. To access it you have to email Microsoft.