Asterisk & Virtual Modems

Has anyone heard of a product / project to create virtual modems within * to allow users on the LAN to connect to a virtual modem and dial out over the PSTN ?

I have a customer who uses modems to connect to remote devices for management. It would be very cool if each user could install a client on thier PC that installed a virtual serial port that in turn connected to a software modem within Asterisk.

Any ideas ?