Why Fax won't die is a decent article on FastCo. It is still a big opportunity. Now bundle efax with there ideas: document management, paperless office, file search and retrieval, data storage and more.
Take the technology out of the way of your customers. Remove it. Offer it as a service like Managed Print
Usually people worry about the price. Screw it. If you explain the service, the pain it solves, how it will deployed and how you will handle the services, 60% of the people you talk to will take it. (40% will shop it or ignore it or put it on the burner.)