Just my opinion, but there will have to be many small tags that transmit available. Obviously new drones will comply, but this isn't just drones. There is a huge segment of DIY people, by that I mean, drones, gliders, planes, helicopters, paraplanes, model rockets, etc. Not all of what I've described are RTF or BNF. There are still a lot of builders / DIYers out there that will need to comply. I don't believe it's the intention of the FAA to ground everyone.
For example, when you buy a receiver it will eventually include the tag with Bluetooth and or WiFi.
I think how the technology will work is still an unknown. I will infer the tag may be a data logger / black box for law enforcement, so when needed law enforcement will need Bluetooth or WiFi access to your logs so once they have you land, confiscate, or recover a crashed drone, they can access the owner info and flight logs.
I don't see how a live Bluetooth / Wifi connection would work so when people say anyone in the public can monitor your drone, I don't believe that. Bluetooth needs to be bound, so does Wifi. Both have limited range, so I don't see live monitoring being what they are after here.
I've also heard people say private property should be a designated exempted zone in addition to authorized flight fields. My problem with that is that private property doesn't matter, the FAA in the United States already has jurisdiction over the airspace above private property.