AIS (Automatic Identification System) has been a nice addition to the boating world. It provides a chart with ship and boat locations as well as info about the vessels. Many recreational boats have them as well as the big ships, which are required to have them. You can download Shipfinder for both iPhones and Android. It has saved me a couple times on the SF Bay. When I see a ship coming thru the Gate, I fire up SF on my iPhone and it tells me which port the boat is heading to, speed, origin and what type of credit card the Captain uses (kidding about the last one). Anyway, if the boat is heading my way, I can take evasive maneuvers way before it gets close. With these monsters moving between 14-16 kts, it's nice not to have to tangle with them. I also got into a foggy situation in the middle of the night and it was great to be able to "see" what was around me. Combining that with my nav app, iNavx, we knew where we were in relation to Alcatraz and Angel Island. Peace of mind is a wonderful thing. If you sail a bunch or if you get out only a few times a year, this is a great app to have in your back pocket. You must have cellular reception for this to work on your phone. I plan to install a real AIS package on my next boat for our sail to New Zealand. There are two types of systems. One is just a transponder and the other is a receiver and transponder. I hope to get the latter.