Using the messaging module for multiple / group recipients

I have a client project and they are keen to use the messaging module to allow communication between groups of people who belong to Committees, to workgroups, project boards, etc. Looking at the out of the box module, it appears that you can only send a message to one person at a time - is that correct?

Ideally, the client would like to set up groups of users according to their membership of / or linking to a Committee / Project, etc. and one person would be able to send a message to all people in the group (like an Outlook Contact Group) just be selecting the group name. The main difference with Outlook is that as contacts are added / removed from the group, this is automatically updated so the person sending the message doesn't have to worry about managing the group.

Any ideas?

Tim