Sentry Gun Prototype 1 (SG1)

Yes many sentry gun projects exist, but not one designed by me. I have a keen interest in embedded development and especially robotics and have decided to keep my embedded skills sharp by developing  the SG1.
Initially the SG1 will provide only a simple manually controlled XY platform i.e. a platform that can be commanded to pan and tilt to an XY coordinate. Later the XY coordinate interface can be coupled with an imagine recognition system that can output XY coordinates.
Now I don't want to spend time developing hardware, especially when this is not necessary. So first off the SG1 will be developed on Lego's Mindstorm NXT 2.0 where time can be spent on the behaviour and software.

There are many software platforms/languages available for the NXT including: C, Java, ADA, BASIC... to name but a few. Also there is a couple of graphical programming environments including Labview.
I want to sharpen my Java skills and although I am very proficient with C, I'd prefer an OO environment - so Java will be used.