Sarin
I believe Zulus work (ANR,Bluetooth,cellphone music etc.) with panel power option or battery power option as long as they are plugged in to A/C panel.
I don't believe they work unplugged from the aircraft panel, for example no music from ipod etc. or cell phone usage when unplugged.
This may or may not be a concern but it will affect cell calls to FBO, FSS if dispatch etc if it bwcomes loose or unplugged.
At least one popular brand works with batteries whether plugged to a/c panel are not.
I think Zulu makes adapter for GA to panel plugs.
Whatever you choose Im sure it will be a exceptional gift.