I made the prototype this afternoon:
The string is attached to the ring. The tag was just printed on the computer and I stuck little diamanté in the corner. I bought the rings off of ebay (about £2 for 18) and the tags too (£1.50 for 50!). Not too bad price-wise and something a bit different (I hope).
This is the start of the rainbow ripple - 6 rows in :D I'm enjoying it so far, I do love rainbow things!