911 / black box phone application idea

What if there was a phone ap, perhaps built in to every phone, which turned your phone into a voice recorder as soon as you dialed 911? Perhaps even the recording would be uploaded to a server instead of stored on the phone. This would be like having a personal black box voice recorder like on a plane. The recording would start as soon as you dial so would give a document of what happened before the 911 operator answered and a back up of the call itself.