A couple of years ago I installed an AIS receiver in Sin Tacha, and, connected to my GPS and laptop running Memory Map Navigator, it provides real-time position information on ferry and large shipping traffic. My position is also on my screen, and each target has a 15 minute position vector indicating where it will be at that time. If any of these vectors cross mine, an alarm rings to warn of a possible collision.
As I frequently cross the busy traffic lanes along Juan de Fuca and Haro Straights, I find this little device provides valuable information, allowing me to navigate away from danger involving large ships, towboats, and ferries. Even larger pleasure boats are now using AIS transponders to broadcast their positions. My unit is a receiver only, and does not advise other ships where I am.