Well, here’s a novel use for bioengineering: culture a bone sample to grow onto a toroidal scaffold, and you can give a loved one a ring made out of your own bone.
Of course, after you die, you could also have your cremated ashes made into a diamond, and then set in that ring.
Nothing like saying “I love you” in an extreamely creepy way. Makes Billy Bob Thornton and Angelina Jolie’s idea of matching tattoos and vials of each other’s blood seem Victorian in comparison.