Apologies if this is an old chestnut, but I went out today with the "Boat Beacon" app and was quite impressed:
- Using one of the AIS tracking sites my wife was able to track us from work
- We could see all of the other traffic
- We got an alarm that the CPA with a fishing boat was less than 0.1 nm
Usual things about using an iPhone in daylight, etc., but it worked OK. Obviously, other traffic couldn't see us via AIS.
I have an account at Live Ships Map - AIS - Vessel Traffic and Positions
and just as I crossed the bar it sent me an e-mail to say my boat had just left port; the same on our return.
Clever stuff, this technology malarky!