What an awesome tip; thank you! Exactly the kind of solution I was looking for.
Thank you for this tip. It worked out perfectly without any added wiring.
One piece of advise is it seems its polarity specific so be sure to plug the add a circuit in the exact orientation as the picture, also put the fuse in the same socket closest to the wire. I did it the wrong way and it kept my radio on instead of the 12v sockets. Hope this helps anyone that runs into this issue
Thanks for this. I had the radio-turning-on issue and following this helped me.