We discovered these when we were planning to travel by sailboat.

 We carry a set with us now.

If you do anything with your spouse that involves moving, coordinating, loading, deploying, etc. anything mechanical or in a high noise or seperated-by-distance environment, you need a set of these.

Marriage saver headsets: http://www.cruisingsolutions.com/headsets.asp

Mariner 500 Head Sets