This is the Horn Bike iPhone case from Bone, and you can probably guess from the name exactly what it does. Your iPhone 4 slides into the silicone sleeve and a Velcro strap secures it to the handlebars of your bike. So far, so ordinary.
The neatness comes from the ‘horn’ part, which is in fact a horn speaker that channels the sound from the iPhone’s speaker forwards and at the same time stretches it out, making it up to 13dB louder. Not only can you now use all manner of cycle-computer or GPS apps, you can also listen to music, or hear turn-by-turn directions.
The Horn Bike will cost $30, which is pretty standard even for a non-bike-mounted, non-horn-sporting case, which leads me to conclude that it is a bargain. Now all I need is an iPhone. Unless anyone knows of an iPad bike mount, that is?