I actually think they are kind of cool.
I ferment in 10 gallon cornies so I either have to reach my hairy arm way in there with a wine thief or use CO2 pressure to push a sample out through the liquid QD. I can do both, but it'd definitely be easier to just shine a flashlight in there and check which balls are still floating.
I agree that the default range is pretty useless. I wouldn't mind having a set calibrated at 1.016, 1.014, 1.012, 1.010, and 1.008. Not that I'm actually going to spend the money on them, but I could definitely see them being useful - provided they actually work of course.