Testing, Testing... Are you sure your radio works? Shakespeare's ART-3 Antenna Radio Tester ($125) plugs in between your radio and its antenna and can run a complete diagnostic test in less than a minute. Unlike previous marine radio testers, it can test the receive function as well as a unit's transmit power and antenna efficiency.
Extend a Hand. You can significantly extend the range of your handheld VHF by attaching it to the outside gain antenna used by your main radio. An antenna coax switch (www.gold-line.com) connects your handheld radio to your boat's VHF antenna. An adequate length of coax cable and an external antenna adapter from your radio's manufacturer will multiply your range from most anywhere on the boat.
Back It Up. Don't lose your library of waypoints. Many chartplotters accept blank SD or CF size memory cards such as those for camera, computer, and personal audio products.
360-Degree Vision. Wish you had eyes in the back of your head when backing down your boat, or have the need to run down to the engine room to be sure there's no smoke when engine gauges or alarms start to misbehave? For less than $100 you can get a palm-sized videocamera and connect it to multifunction displays, monitors, or even TV sets and view any spot on your boat.