After trying a bunch of different methods, I also found that writing first drafts by hand is still the most productive approach. Writing is re-writing, right? Type it into a computer later for editing. You'll have best of both worlds (for way less money).
I agree that when you are really into your project nothing "should" distract you, but none of us are perfect. You google one thing and you suddenly find yourself replying to an email 15 minutes later. Our technology influences our behavior despite our best intentions.
I've tried the Alphasmart NEO as well. It does exactly what this does for much less, however, you don't have cloud backup--you transfer the text with USB. Not hard, but another step.
Another option is to buy a $10 typewriter at a thrift store, a $10 ribbon online and then use a $10 OCR app like Prizmo to transfer into the digital world for editing.
Couldn't they come up with a better name than Hemingwrite? It's kind of embarrassing.