Why not give the robot some of the functions that astromechs, within the Star Wars Universe, have - or, at least, real-world variations. Fire extinguisher - easy... if you don't mind only having a couple of short bursts... Welder - not easy - lots of power, plus a lot of fine coordination, touch perception, and delicate sight processing required, although a small (~ 5 Watt) soldering iron might be possible. Two big functions, however, do lend themselves to adaptation.
Firstly, astromech droids, such as the R2 and R6 series, are starship engineers, albeit dedicated to repairing said vessels. Additionally, the R4 series are specifically programmed for working with land based vehicles. The obvious real-world version is to have an OBD-II interface. For those not in the know, OBD-II stands for "On Board Diagnostics (version 2), and is the standard diagnostic interface for car engine management computers, since about 1994 (or so). It may not allow my droid to change the oil in my car, and I think my car is just a little older than OBD-II, but it's something...
OBD-II interface board, circuit board Silicon Chip, Feb 2010.
OBD-II interpreter chip by Elm Electronics
Of course, the board as it stands could do with a couple of modifications... I'm going to add optocouplers between this board and the board to which that I connect it, particularly removing the leds that signal to human eyes that something is happening. Software is something else, of course, but...
The next application is having the droid actually doing some orbital mechanics - what use is an astromech if I can't get it to calculate orbits and navigate from Earth orbit to somewhere else in the solar system?
