The iAcoustic from aBite Design: an analogue amplifier for your iPhone/iTouch. aBite sez:
iAcoustic remarkably boosts the audio output from the iPhone or iPod Touch built-in speaker up to about 60 decibels without using any external power sources. While passing through its wind instrument type horn and solid wood base, the audio source is transformed into warm, rich and resonant sound. iPhone/iPod touch can be charged while you listen if a charge/sync cable is fed into the path-through slot on the wood base.
You have to make a ‘personal enquiry’ to know the price. Which would suggest that it ain’t cheap.