(merged with the existing thread. also, there are a few more anecdotes over here.)
if you value your instruments, and if they’re not easily replaceable at any store at your destination, then never check them. always put them in your carry-on bag. if you’re really worried, carry on enough gear, or a laptop and headphones, to give a musical demonstration. depends on where you’re flying to, really. most of the time, monome devices don’t seem to attract much attention.