This amazing portable silicone mini speaker amplifies the sound from
your iPhone by up to 15dbs (feels like 2-3 times as loud) without any
batteries. It uses old fashioned horn or megaphone technology. Holds
iPhone vertically, horizontally, and has opening reserved for charger.
It also works well in hands-free mode. Works only with all versions of
the iPhone.
http://www.finerthingsonline.com