We use hylafax (formerly flexfax) to send email and any other things
through fax. We have a procmail filter setup that takes To: addresses
looks up the <user> portion in a fax database of user->phone number
mappings, and sends the fax (body of the message) to that phone number.
The fax software itself takes care of the conversion from ascii, PS, whatever
to fax format.
Pagers aren't much different.
Doug Hughes Engineering Network Services
System/Net Admin Auburn University