So a very long while ago I watched a lecture from Kristin Paget displaying a technology that she describes as "Guardbunny". I'm not one for frivolous commercial brand names, but what drew my attention was what it does. I won't bother you with any pathetic attempts made by me to explain it in technical detail of how this Guardbunny product works (do see the demo and explanation in the link below for that), but it basically offers three protection schemes: jams signals of unwanted read sessions, makes an audible signal when the tag is being attempted to be read, makes a visual signal when the tag is being attempted to be read (a light turns on).
The demo:
https://youtu.be/HRXb-FZ6WFM?t=40m20s
Anyone who knows this field is probably aware that we'll never be able to (fully) defeat unwanted RFID/NFC interactions, so it would be nice to at least know when our tags are being read, so we can make due changes if the read session was unwanted. Therefore the latter two of the three protection methods sounded very intriguing.
Would it be possible to build in a system in future ring models that makes an audible and/or visual signal when there's a read activity in progress?
As you could see in the demo, it doesn't require any extra power or such, but probably boils down to matters of available space in a ring design, cost, and having the required technical know-how to implement.