GSI Quality Mini Boom-Box - Weather Resistant Transparent Case With Built In Stereo Speaker And Volume Control, For Apple iPhone, iPod And Mp3 Players - Play Music Outdoors On Patio, Beaches Etc. - Black
My iPhone fits in it perfectly, it's quite loud when turned up and pretty well sealed.  It has some distortion in it when turned up loud but I would expect that from speakers that small.  The speakers do make that weird phone dada dada dada dada sound when the phone \\"talks\\" to the network. I think it will be perfect for strapping to my 4-wheelers handle bars or tucking into the mesh pocket of my cooler.