The video demo of EARs ($3.99) is quite impressive. It lets you use your iPhone as a hearing aid — including a range of adjustments to help accommodate your particular needs and the particular environment. You manipulate the tones by dragging two dots around the screen, even having the ability to tailor the sound to the specific needs of each of your ears. The app picks up ambient sound in real-time, either using an external microphone or the built-in mike, processes the sounds, and then sends them to your earbuds. It works best for people with mild to moderate hearing loss, but is also helpful for people with normal hearing in situations when it's hard to hear. It seems like quite a cost-effective solution, compared to the thousands of dollars that it costs for hearing aids. The only downside to this solution is that people will think you're not listening because you have earbuds in your ears.