This would be cool. I want an R2-D2 to chase my kids around with. Mount a retractable tazer or cattle prod on it, and I would be all set to Battle Buzz-droids full on! This actually looks like it would be a blast, and surprisingly not that difficult to do. astromech.net has an excellent parts list and a ton of tutorials on how to build this spunky little droid, and while some parts are over the $400 mark, very few are much more than $150. So inside a year or so you could gather all of the parts and slowly build it.
Add your remote control, or hey I know, bastardize a RoboSapien for the remote and programmability and use parts from it to be able to add a some memory and routines to it. Of course, having not read all of the details – it might already be built into some of the designs. Bet your kid would win a Science fair with this.