Well, you would certainly get a longer battery life with the phone sized form factor. I would assume that you aren't going to have it in scope mode all the time though so the watch should last much longer. Then again, I don't want to have to charge my watch a couple times a week.
It is a cool design. I went through the webpage and it might appeal every EE. But does it make a business case?...I don't think so. Why would I need a scope/waveform generator in a watch? Again, talking about the power it takes, "When using the oscilloscope, the battery will last about 12 hours"...does it make sense for it to be in a form of an watch? Why not a pocket oscilloscope in the size of a phone or perhaps using the phone, with better specs & a bit bigger display, with more buttons/nobs? Would it be so difficult to carry if it comes in the size of a mobile phone?