John, my understanding is that it works through DSC polling not AIS.
So if I set my GPS up with each of your MMSI numbers and ask it to track it will continually send position requests to your radio set and assuming you accept the polling request I will get a DSC reply that includes your position data taken from the GPS and display that position on my set.
I can set mine up to track the whole phone book of MMSI numbers and assuming you have a DSC Polling capable VHF linked to your GPS you should be able to set yourself to automatically accept polling requests saving you the bother of stopping to see what the screen is beeping at you
Seems someone even does a bit of software to show it all on a puter so someone clever could add that into a widget to show up realtime on the web if they wanted.
So to get the system working you just need.
DSC radio capable of accepting polling requests.
Automatic acceptance of polling requests.
A GPS linked to the Radio.
An MMSI number.
A race entry that includes your MMSI details before taking to the water.
I'd bet that you've all got that anyway with maybe the exception that you haven't registered your sets and if you haven't got it it's not a lot of money for something you are going to use anyway.
The final advantage is that you can talk direct to individuals and this would have been a boon at Harwich. We never had a single radio contact with race control as the frequency was being used by the inshore safety teams and was full for the entire race.
Our radio reception anyway was crap as we were some 30 miles off the base station with their antenna obstructed by the horizon / land / junk. My understanding of a DSC conversation is that the digital element not only allows better penetration of the signal but that the conversation is heard by only the 2 parties involved over channel 70 so not interfering with the race / safety channels.