Voice controlled Cell Phone

  On my cell phone, I'd like a sensor which recognize my voice and automatically picks up the call if i say any particular word Like "hello" or "hey." Especially when I am driving or busy in kitchen. Also, it would be nice to disconnect the call using any word which has been already recorded in the phone sensors.
We have seen cell phones with a touch screen. Now I'd like to see a phone which is only voice activated. It would really help people to drive safely and enjoy talking while working.