I don't know much about computers, but people who are computer savvy have said it is quite easy to rig a monroi device, have it give its recommendation and if there's a TD around, to revert back to its regular mode without anyone being the wiser, including the opponent.
Why introduce this into the tournament hall at all? The complaint that some 8 yr old kid can't write his moves and therefore needs an engine to write for him just doesn't make sense to me. My 8 yr old students learn to write the moves. It's not hard to teach them that much.
And even if there aren't many who are savvy enough (I know a few :p) when you start talking about big money prizes it can bring out the worst in people. They'll cheat even if it's difficult. Even if they don't know how to play chess. And it only takes 1 to ruin the competition for the others. As you're saying here it makes no sense to tempt people by making it easier. We should be making it harder.
I believe if you are unable to notate your moves, you should be forced to play the game blindfolded and you have to have your ears checked.
Otherwise leave the tournament, you shouldnt be there to play tournament games. Those with dissabilities should be allowed for some special exceptions.