A PLB (Personal Locator Beacon) is a must have whether you are flying over land or sea. It transmits both on 406 MHz to the satellites above and on 121.5 MHz so that SAR can track your signal as well it sends you GPS position.
This ACR MicroFix II is a third generation PLB and it costs $599.99. It can make the difference of a long wait, if ever, for a rescue and a quick find by SAR.
Pilots flying without such an emergency device attached to their person should rethink their emergency procedures.