I feel like it's unnecessary...
This is my opinion so don't just take my advice.
1. If you're already carrying something, that's more weight on you.
2. It doesn't look very comfortable.
3. I'm a fan of 2 U-locks (1 if I'm not gone for a long time.) rather than just a thick heavy chain.
4. It looks like a seat belt!
5. Super pricey.