Video shows off Samsung Galaxy S4's Air Call Accept for almost any Android model
Now, you don't have to own a Samsung Galaxy S4 to use Air Call Accept. A free app from the Google Play Store will let you wave your hand over the proximity sensor on your Android phone and have the phone respond exactly how the Galaxy S4 does. There is both a paid version of the app along with the free one. The paid version of the app gives you the option to ignore a call, turn on the speakerphone automatically when you answer the phone, and send an email when you reject a call.
The app is available from the Google Play Store for those sporting an Android powered handset running Android 1.6 or higher, and with a proximity sensor. Now most Android users will be able to answer their phone when it rings, no matter how dirty, greasy or wet their hands are.
source: AirCallAccept via RedmondPie