This document from Microsoft on Server Core indicates that you can perform the following steps to enable read-only remote access to Device Manager on a Server Core installation:

• Device Manager. You must first enable the Allow remote access to the PnP interface policy setting. To do this, on a computer running Windows Vista or a full installation of Windows Server 2008, open the Local Group Policy Editor MMC snap-in, connect to the computer running a Server Core installation, navigate to Computer Configuration\Administrative Templates\Device Installation, and then enable Allow remote access to the PnP interface. Restart the computer running a Server Core installation.

The problem is this: I have been unable to find any way to open another computer's Local Group Policy via gpedit.msc.  I've looked at Windows XP, Vista RTM and SP1, and 2008 - all to no avail.  The solution is to create a domain-based GPO with the above setting, and then either reboot Server Core, or run gpupdate /force to force updated processing of Group Policy.  With this policy in place, you can successfully open a read-only view of Device Manager.

I don't recall when (if ever) gpedit.msc has been capable of opening another computer's Local Group Policy remotely, so if someone comes across a way to do this I'd appreciate hearing about it.