They have to be turned over when the demanding branch can articulate a compelling need for the information to fulfill one of its own constitutional functions -- a need that outweighs the executive branch's interest in confidentiality.
The BTM8 is begging to be taken on your next picnic thanks to its carrying handle, while the BTM5 is palmable orb with one up-firing speaker for when you need a speakerphone in a pinch.