They say there is an app for everything, now there is one which allows you to use your phone to help locate someone who has fallen overboard. I have not tried this and can’t quite come to grips with the idea of using ones phone to carry out a primary life saving function, but if you have an iPhone and want to give it a spin it is at the iTunes store.
If you are looking for a device which is designed to be worn the Kannad R10 is new on the market and works with the vessel’s AIS system.
The R10 is the first device I am aware of that does not require a dedicated receiver on-board your vessel. For under $300.00 you can equip a crew person with this device which has a typical range of 4 nautical miles and transmits a unique emergency alert to all AIS receivers and AIS enabled chart plotters within its range.
While the iPhone app is less expensive, I would put my money into an R10 if I really wanted to be rescued after falling overboard.