There exists 'smart bands', which can be applied to any (generally non-smart, obviously) watch that uses normal pin-style watchbands. They have a contactless chip in them that can store one card.
My traditional watches use them, though I had to custom-make one of the bands to be in a style I wanted.
It's a major use of the watch for me also, but something like a Pebble 2 HR would tempt me to abandon payments.
Do you have any links to examples of these bands you've found useful?
My (Timex Pay) one seems to function using a virtual card (remotely lockable) provided by the bank, which uses some sort of tokenization-based security chip on the band itself. I imagine there's probably some security flaws because they provide the NFC encoders to the user. It's backed by https://tappytech.com
I wouldn't count on that, getting every bank on board is a massive undertaking. Even Garmin Pay and Fitbit Pay (before it was folded into Google Wallet) have/had huge gaps in their coverage, especially outside of the US.