Don't worry too much. Most sharks including the GWS here in Perth are vegetarians. honest.
As for electronics attracting sharks I reckon it's a myth(ish), but definatly nuffing to worry about. If it would be true then the same would be true for your computer, bottom timer, (video) camera etc etc.
So the divers in SA use kisses, or no Rebreather's at all?
Denz.