When I was younger I remember a friends house had a intercom system that was built in that worked everywhere.  If you wanted to get a hold of someone just press a button, even had a phone patch.  Even though that later might not be perfectly useful, it was a nice touch.

Now that Cisco has all the good stuff from the early 2000s you can get it pretty cheap on ebay. 

So if you wanted a whole house phone/intercom system, this is the project for you too.

THe problem with this system now is that cell phones on WIFI have pretty much eliminated the need for this system. But it will still be neat to figure out how to do it.

The system I want would have the following:

A backhaul server that can take normal VOIP or POTS to the aggregated system.

Call forwarding

3 way calling

hold

music on hold

transfer to another phone

Research so far:

Things to research:

Call Manager

ATA hardware

VOIP phones

WIFI VOIP phones

DECT VOIP phones