That price is good but you also need a way to display the data. Most newer chartplotters will display the AIS data, and let you set a CPA (closest point of approach) alarm.
My chartplotter, vintage 2005, does not handle AIS. Therefore, I chose instead a Standard Horizon VHF with built-in AIS receiver It does the display and alarm functions. It also has a remote microphone with AIS display in the cockpit where I need it. But it does not transmit my AIS info.
You can also use a laptop PC based chartplotter for display and alarm. I rejected that as too much of a power hog and too fragile to have a laptop operating 24x7.
Caution: Some skippers report that their AIS transponder/chartplotter combo continuously give alarms that you are about to collide with yourself. Both the AIS vendor and chartplotter vendor point fingers at the other guy, leaving the poor boat owner stuck with no solution.
