Possible Clues:

• It might make a private remark public
• Liability on a lapel
• Cause of a public embarrassment, maybe
• It'll pick up the faintest of noises
• It might capture an on-air gaffe
• It might pick up a whispered comment
• It might pick up an embarrassing remark
• Device that may catch a private remark
• What might catch an embarrassing sound bite
• Source of a scandalous comment