NFC add-on

[mitcoes]

Unless you can get the banks on board it can't happen. Given their reaction to rooted Android phones I don't see them supporting a phone where the user can rewrite the firmware.

No need to get the banks on board.

Just one - debit and credit card compatible payment method - as PayPal
that would see the enormous advantage of having the cheaper watch NFC for payment
at their service.

And for security measures, they can help funding new ones.

[DrYak]

(e.g.: so the watch could communicate with continuous glycaemia monitors like this, for which there is already opensource code available)

Update:  I don't have a usecase anymore needing to hack NFC into a tiny device with a screen - by now, a lot of the continuous glycaemia monitors have switched away from NFC and toward BLE protocols.


NFC/RFID on a smartwatch could still have other applications simple to deploy locally without need to involve complex banking certifications. E.g.
Using RFID tag stickers as "non-powered smart button" - tap the smartwatch against a tag and the watch sends some signal to home assistant to trigger complex scripts (See this tweet as an example)

Or using RFID-like function from the watch itself as an entry card for some facilty, etc (Swatch has had the Snowpass function for year, e.g. this had one).