Show My Car Insurance
The Apple Watch includes the Wallet app from the iPhone. This means if you add a card or pass to the iPhone, you can also show it on your Apple Watch.
I use this to carry my insurance card with me at all times. I drive a lot for work in a wide range of cars and if I need to prove insurance when I run a quick errand I have my insurance card on my wrist at all times. This is handy if I forget to take my wallet with me and leave my phone at home. I've done this a few times now that my Apple Watch has LTE so I can always stay connected.
You'll need to install your insurance company's app and then if they offer it add the insurance card to your wallet on the iPhone and to your Apple Watch.