For shutting down multiple DOMU's i have found this excellent solution ( I knew I had read it somewhere ) :
APC UPC Deamon
http://www.apcupsd.org/

So what to do :
1) Install apcupcd on the dom0. With Suse this is available through the portal.
2) Setup the dom0 as apcupsd server by editing the config file :
NETSERVER on
NISIP 0.0.0.0 ( this is to listen on all ethernet cards, you can also specify your internal network ip )
NISPORT 3551
3) Check if the local machine works, by starting the deamon.
4) On the domu's install the same with :
UPSCABLE ether ( connection through ethernet )
UPSTYPE net
DEVICE server-network-address:3551

And volia ! Your done.
Work on both Linux and Windows.

More info can be found on :
http://www.apcupsd.org/

Good luck, Stephan