While I do not mean R2D2 exactly, I do mean his functions, more or less.
R2D2 interfaces will all the various computers and devices, stores and plays back information, repairs systems, and so on.
While a lot of it is merely science fiction/motion picture device, there is some utility here I think.
A universal remote control. How many devices do we have that their own remote control interface. Surely a robot should be able to use voice interfacing and a library of remote control signatures to control various appliances.
Vacuum cleaner, well obviously.
Standard computer stuff, word processing via dictation, music, video playback, etc.
Rocking the babies cradle
and so on.
I think a viable application of a mobile robot is not necessarily something "robotic" any more than the first viable application of personal computers was something "computing."
The first personal computers became popular not because of "computing," but because the could do something mundane like be a better typewriter (word processor) or better adding machine (spreadsheet).
Maybe robotics is similar, the robot isn't going to get popular because it does something "new" and "robotic," maybe they get popular because they do something mundane.