I have a little amplified speaker. It runs on 3 AAA batteries. Where to mount it? How about on top of my helmet?

OK, today, I tried it using packing tape. Not very elegant, but it pretty much worked. I kept my iphone on my belt. The audio cable goes down my right side, through my back belt loop, and around to the holster on my left side. Excess cable is stuffed in my left front pocket.