Transparent lavaliers also work well as hidden mics in the set. A mic in the centerpiece can give you a restaurant table. A mic in an executive pen set can pickup both sides of an across the desk encounter. A mic on the inside of a doorjamb can give you that short line from a passerby poking his head into the office. A telephone booth is a snap to rig.
Someone reading directly off of a blackboard or bulletin board is perfect for a hidden lavalier.
A danger of using lavaliers is to forget to take perspective into account. A proximity lavalier always sounds like a tight close-up, even when the camera is fifty feet away. Transparent mics sound much more natural, but unlike boom mics, their perspective is fixed. One quick fix to the perspective problem is to also deploy a shotgun mic directed at nothing in particular. Another trick to open up perspective when using lavaliers is to place them a little further down on the chest than normal.