I would love to be able to implement this type of feature, however I am dealing with small businesses with at most 15 people (so far) and no on-site IT staff that could setup the server and ports. As it is, we have about 1/2 of our clients using an XP workstation as a file server. I'm not looking forward to explaining to people how to install SQL Express and opening ports and starting services just to be able to connect in this environment.
Part of this is related to the installation. We have a VERY sophisticated install so that there doens't have to be IT people to install SQL Server, etc. This is all done through the installation, including the installation of the service, ports, etc. The more sophisticated you make the install, the less sophisticated the end-user has to be to install the product. We have spent a TON of time here...but it has paid off in the end.
In this example, it doesn't have to be a server OS...we have users that use XP and peer to peer as well. We just have our own Server service that runs (on any Windows platform). Just some ideas 