I'm not sure, but I think this mech was supposed to be available in ME2 for purchase, or at least there's references to it in the ME2 files (right under where it mentions about buying Prejek Paddle Fish, it mentions about buying it "Do you wish to purchase Sparky"). It got cut for some reason.
It's only an assumption on my part, but perhaps it was because they thought people would rather a companion robot dog, similar to the dog in Dragon Age. That, or they simply couldn't implement it the way they wanted to by the deadline and decided that it would go into ME3, instead. As far as I can tell, this robotic dog in question gets delivered to your cabin after it is purchased, so I have no idea what use it would be other than the same as the fish or the hamster (though, the hamster is called "Boo" in the files, so there's a BG reference there).
The robotic dog in ME3 can be brought on missions. So it's more than just a pet to keep in your cabin. Should be interesting to see.