One of the biggest weaknesses of iOS devices is the speakers. There are plenty of products out there designed to amplify the overly quiet speakers such as the db4 case, the Koostik dock, and the Horn Stand Amplifier. A new player is entering the field called the ampjacket. Not only does it work with iPhone 5, but it's available for iPod touch and iPad mini as well.
The ampjacket uses precisely tuned audio channels to guide and amplify the sound output from the device's speaker. Other cases on the market tend to just direct the sound forward, which does make it slightly louder, but ampjacket's makers claim that the patent-pending design actually enhances volume and clarity.
The channels on the case will, of course, make the device a little thicker, but it's certainly more space efficient than carrying around a separate speaker for the devices. The cases are made with a soft shell thermoplastic polyurethane (TPU), so it is able to protect your precious devices while it amplifies the sound.
The iPad mini version of the case is built to work with the Smart Cover, so you can protect the back with the ampjacket and the front with the Apple's Smart Cover. On top of that, the sound channels can actually be used to lock the Smart Cover in place, which makes it useable as a stand for the iPad mini.
The cases are available now at US$24.95 for the iPod touch model, $29.95 for the iPhone 5 model and $39.95 for the iPad mini model.