I won't use my smartwatch also for this purpose. I have one, but when it comes to my crypto portfolio, I won't take the risk besides it is too hard to use the smartwatch even when you are copying the btc address to another site. The screen is too small for me. And with the bluetooth in use, this is very easy to penetrate with. I even don't use my smartphone in my crypto transactions. I still prefer computer or laptop to do my transactions in the web.
I read "crypto portfolio" and this popped up in my mind. A smartwatch app for cryptocurrency portfolios would be a good idea. There'd be no information at risk except balances.
Now regarding the Bluetooth part, I am very curious to know how vulnerable a smartphone with Bluetooth turned on is. If you're using some smart gadgets, be it airpods or a smartwatch, you always have to keep your phone's BT on. But I guess phones' security can not be compared to a smartwatch's..