Technically not an amp, but whatever.
I wanted to listen to my music in the shower but the iPhone's speaker would get lost in the noise from the shower. So I directed the iPhone's audio straight towards me. Worked pretty well. Just ask my neighbors.
It's more of an audio focuser (if there is such a thing) than an amp.
Edit: welcome TUAW readers. See also: cameron i/o, my website.
Oh, and P.S. it was Charmin ... I think it was the big roll, not the "Mega" roll. Although I don't know if it was extra strong or extra soft. We threw away the packaging.