If you have an alpha numeric paging system that can be paged through e-mail, then you can set a rule with inbox assistant to forward all incoming messages to the pager address. For example, my pager number is xxx-928-0903, and to e-mail page it is xxx9280903@mypagingcompany.com.
In Exchange Admin, create a custom recipient called ‘username Pager’, and type PAGER. You will have to know what paging system they are using (Ameritech, PageNet, etc.), because different systems require different settings. You can get the information you need from the paging system provider. Once the account is created, users can individually send messages to the pager accounts, and/or set their e-mail accounts to forward to the pager account. (I believe that the Admin can do this as well.)