Griffin's AirCurve is an attractive little block of acrylic that looks more like a science demonstration than an iPhone accessory. Using the age-old technique of passive audio amplification, sound is captured from the speaker and fed around through the nautilus-shaped chamber. The results are loud and clear.
There's a pass-through for the USB cable as well. If the idea of amplifying the simple mono speaker on the phone isn't palatable for your musical listening tastes, the louder alarms and ringtones should be. We tried it out in a noisy convention hall. Without it, the music was barely audible, but once set into place, the music was clear as a bell. It's available now for $20.