Interesting device and solution! I like it. I just happened to get a great deal on the basic Miwaukee drill/driver set with two batteries and a charger. After that, getting any other tool that fit the same batteries just made sense... and the tools have held up really well over years of moderate use. (I tend to go building-crazy for a couple of months, and then build nothing for several months.)
Yeah you buy into a battery system more than anything else. I find that most power tools suffer from "dive knife syndrome" - the only thing you need it for is to tap the pommel on your tank to get the attention of other divers and mmmmmmmmmaybe use it to pry something up or cut something you're tangled in. Ideally it's got a blunt tip and is bright yellow or orange so that when you drop it you can find it. Yet most dive knives, because they're bought by weekend warriors who think they're Navy SEALs, look like this: The average consumer drill looks and acts like something you would use to single-handedly assemble a motorcycle crate with, when really, 90% of its functionality is swag hooks for your wife's fuchsia baskets.