ShakeCall is an Android application that links your answer/end call function to the motion of your phone; you can simply shake your phone to answer or hang up.
After installing ShakeCall you can configure it so your phone picks up calls when lightly shaken and/or hangs up calls when lightly shaken. It also supports proximity sensors (although not all Android phones have them). For those with proximity sensor equipped phones the phone will automatically accept or end a call when you bring the phone up to or away from your ear.
ShakeCall is a free application, hit up the link below to read more and grab a copy for your Android phone.