Replacement for Alerter / Messenger

Hi,
Previously there has been the Alerter and Messenger services for broadcasting messages on a network. The use of this has effectively been stopped due to spam.

Is there another way to broadcast messages? The purpose is for admins to be able to convey critical messges such as "Server Reboot in 5 minutes". With so much email everywhere, email is not a good solution as many people will not read the mail until much later. Preferably there should be a method to select who to send to, such as by domain, IP range, computer names, Outlook distribution lists etc.

I am not looking for a full solution now, but please point me in the right direction so I can research further. (This is why not so many points are offered)

Thanks!
/DanStart Free Trial