I would like to have pbx features loaded onto it for intercom. If that could come pre-loaded with some service provider API that would be preferable. When companies like Google host your telephony service under an ASP model in the future, these APIs would be as easy to integrate with your residential gateway as the present day carrier pre-selection.
Anyway, apart from pbx features and pre-integrated service provider APIs, I would also like the gateway to support WiFi so that those family members with WiFi phones can call from their rooms. Or if there is an incoming call, we can transfer calls with simultaneous ring on fixed extention as well as the WiFi phone extention .... and do other 20 odd things with it. If the family members are able to pull up the buddy lists on their WiFi phones and use presence based applications through the residential gateway that would be even better.
I would also like my residential gateway to aggregate access to my electronic gadgets such as the camera, mobile phone, MP3 player, etc. So one chip inside the gateway organizes access with the help of a corresponding standards based chip inside the electronic items. Artimi is working some wireless USB stuff that will be capable of doing this. So something like that inside the residential gateway.