Artist Luke Jerram once designed a projector wedding ring for himself. Before that, he made one for his bride, Shelina Nanji. It's made of silver and engraved with a 20-second message that is audible when played on a special phonograph:
100 lbf/in² of pressure was required to cut the silver ring, using a vibrating diamond stylus. The ring is also a homage to Thomas Edison who made the first sound recording machine - the phonograph in 1877.
Using the ring, I proposed to Shelina in a hot air balloon over Bristol in 2005. We've since got married and had 2 children Maya and Nico.
You can see a video of the ring being played at the link.
Link via Make | Photo: Luke Jerram