Hi there! I'm sorry, I won't post an actual tutorial, but I can give you some pointers on how I did it!
I fact, I casted the little "cubes" with resin (after making differents molds for the different parts) The antenna comme from a little pocket radio that I dismantled, and that I added to the top piece while it was curing.
The actual wristband is made with foam, and I glued the resin pieces on it.
I'm not sure it was the best way to go, but it doesn't look so bad! Hope it helps!
(Yay for Matt Engarde...!! <3)