it's like a sea foamy cascade of beads!Your description is even more beautiful than the charms themselves!
I used little clasps like this, don't know what they're called in English. In dutch it's : veterklemmen.
You can bend the edges over your cord and attach the beads to the little ring.
You can also buy ready made cell phone charm straps, like this (with tute)
Good luck! And please post your results here, i'd love to see other cell-phone beauties