Recently, Google has applied for a patent for double-side switch of the phone calls which means users can receive the call in any side of the cell phone.

From the sketch of the new patent,we can see the top and bottom of the phone can be used as a handset or microphone: when the phone is normally placed,user can use top to answer, bottom to speak; and if the phone upside down, the cell phone sensor will determine the direction of hand-held switch and then the listen and speak part will automatically upside down.

But, this new mobile phone patent is pending approve and need some time.....