just my 0.02 about the korg.
I own a MR-1 and did many stealth recordings with it. Never had a single problem, I can even imaging you can disguise it as a MP3 player; for extended battery life I'm using a self made battery sled holding 4 AA batteries.
It sounds great, is solid and can record in a wide range of quality and formats, from MP3 to DSD.