Having an AIS transponder is another tool in the toolbox which is simply that - a tool. If one is relying on this tool or any other single system to uniquely keep their vessel and passengers safe I would recommend to step away from open water boating for the safety of themselves and others...... The big issue with AIS (and I've used it for several years) is when in a port or other busy areas it alarms constantly for boats and ships that are not running as they leave their transponders active so I tend to disable the system when in these areas and use the other "tools in the toolbox" to safely navigate. Heck, in my marina alone there are three or four non-commercial boats constantly transmitting. In other words, jurisprudence is the key on how, when, and where to use your navigation tools. All of the primary electronics manufacturers have certified AIS transponders available which can use a dedicated or shared VHF antenna. There is, however, not many combination VHF radios with integrated AIS transponders on the market and probably for good reason so I'd stay away from these for now.