Wireless VOIP. Setup a way to use a mobile phone through a VOIP system. Or, embed Bluetooth into a phone and use that to talk with the VOIP system. Something for VOIP that might be interesting, would be finding a way to get a Cellphone to pass a signal to the base phone (VOIP) and then to have the VOIP system read in that information and dial that for the Cellphone so that you pass something likt 544 123 1234 (base station number) 654 654 6543 (number to dial) and the base station dials you up automatically and transfers the call to you. That way you get free longdistance all the time...
Just a thought.