i was looking at the progasm ice with the air bubbles inside and it occured to me if the bubbles were a bit larger
a couple of steel balls could be put in the bubbles so during use they would roll around and create extra stimulation
to the area.
That would be hard to do; the bubbles are accidental voids from the injection molding process, and would be nearly impossible to insert anything in the middle, unless, of course, you had a small transporter device, aka Star Trek.
I suppose you could use a 3D printer and insert a ball in an intentional void, but that process is primarily for experimental prototyping purposes, due to its expensive nature; Aneros devices3D printed with a ball in the void would easily run from $300-$1000 each.