Why was a separate physical device needed for this? It seems like a simple smartphone application would work just as well, if not better as I would assume virtually all of the target audience for this service already have a smartphone.
But with Dash, it's just grab the Dash from whatever convenient location you keep it, speak into the Dash, and put it back. That's easy enough that I would do it, and Amazon would get my purchase.
Unfortunately, Amazon Fresh really kind of sucks (at least in SF), so the whole premise is flawed. Oh well.