I'm sure, but how many others would, vs just using bulky equipment? I agree the analog bandwidth is quite limited here, but it's good enough for audio work, and there's a large potential market there among live sound engineers.
If I can pay $100 for a super miniaturized audio only scope, or the same price for a bulkier 100 MHz scope, I'd go with the 100 MHz scope every time, so in that sense you're right.
That being said, it sure is nice that today's scopes are more like a lunchbox than a boat anchor. My lab at work easily has a million dollars worth of "full size" test and measurement equipment from Agilent and Tektronix, but there's no reason the entire budget has to go to them. We're happy to pay for stuff like this (http://www.triarchytech.com/) when it's a solid product that makes our lives easier.
What benefit does an oscilloscope have over meter+ears when resolving ground loop or crosstalk issues? Time domain information doesn't seem terribly useful.
This device has a few other tricks up its sleeve as well as a basic 'scope; it also does FFT, phase metering, and operates as a voltmeter. I'm not suggesting it's the ultimate device of its kind, just pointing out that there is a class of people for whom having this functionality in a highly portable package would in fact be handy.
Oh, and the protocol sniffer means you can test MIDI output from a synth or sequencer.
I would not suggest that this watch replaces a proper oscilloscope for lab work. For that matter, the great majority of problems are more easily diagnosed with a computer and some decent audio editing software, which will have things like frequency plotting and phase metering built in. But it looks very handy for location work, eg there have been times when I've had to repair a cracked solder joint in a shotgun microphone in the middle of nowhere, and had no way of testing the gear I was working on before putting it back into service.
The one thing that I don't see on it that would be enormously useful (but also power hungry) is a backlight. It seems like you would end up needing to point a flashlight at it in many situations.