Thanks slang800...to add to smt88's good points, phone apps that are supposed to perform a similar function don't work well and reduce the audio quality- as you can see from the reviews on this phone app: https://itunes.apple.com/us/app/awareness-the-headphone-app/... This is due to hardware/app limitations. Another advantage of being a separate device is you have the freedom to place it where you want with an extension, so you won't have the microphone buried in your pocket for instance. Also, it adjusts the alert level to your surroundings after a button press. A phone app wouldn't be as convenient because you would have to unlock your phone and go to the app for adjustment. Lastly it has 50+ hours of life on a charge (rechargeable) and can be used with any audio player and headphones.