Apps are funny things. They tend to provide narrow utility -- focusing intensely on one specific thing -- but once you get used to them, you wonder how you lived without them. Take this Awareness! app, for example: it gauges environmental noise levels, sets up a threshold, and then pipes in anything louder than that into your skull alongside your music. Reasons why you'd want that to happen include oncoming SUVs, mothers screaming because their babies are in peril (from oncoming SUVs), or something as benign as your teacher yelling at you for not paying attention in class. There's a nice set of options too, such as manually adjusting how loud a sound must be to be allowed entry into your cranium, as well as pausing of the app or of your music. Awareness! is available for five bucks on the iPhone and iPod touch, and will soon jump on to the iPad, Android, Symbian, and even the Mac and PC.