Hello,
I had the security people look at it and wonder - once I explained what it was they let me pass in a hurry! But keep it out and handy because they will want to see it.
I would definitley recommend pumping in your seat and not the bathroom - too many people knock at the door which makes it stressful and then not much happens! Who cares if people wonder what the sound is (-:
Good luck - where are you flying to?
Karyn