When you equip this implant/item/ability/however they do stuff in PS2, you can listen and hear enemies with more volume and range than if you had just your normal hearing.
It would be a narrow beam, like a zoom implant.
It would do nothing with your radar. It would just allow you to "audio zoom" a very narrow slice of your view and hear it more loudly. No red dots show up on your screen.
http://www.flickr.com/photos/normko/...57603230869583
However, I think with future technology, we might be able to shrink it a bit.
It would require your environment to be quiet, too, so you can't use this from a plane, tank, vehicle, or in the middle of running or even walking. Standing still, stable, and in a quiet environment, it would allow you to have increased range, in a narrow band, for your hearing, much like a zoom implant.
It also can't hear through walls or doors, so it is used outdoors, not indoors.
It would make physical stealth, such as is important in some real-world combat, a valuable thing. Unlike Audio Amp, it would pick up weapon reloads and other noisy stuff, but it would not allow you to hear enemy soldier's footsteps.
And, it doesn't allow you to hear past a hill, but would be useful for sweeping forests, caves or steamy swamps for sounds.