If you love gestures, you going to love Lumia Gestures, a feature which is beta right now lets you answer calls by just putting on your wears, something we do all the time. This feature is making its way to Lumia Windows Phone through an app which you can install right away.

What you can do ?

Answer a call by picking up your phone and putting it to you ear
Mute your mic during a call by placing the phone on a flat surface with the display facing down

Put the call on speaker by placing the phone on a flat surface with the display facing up
Silence incoming call ringer by flipping phone display down

The gesture works vice versa which means if you put it back on ear after you kept it on table, the speakers turn off and switch to normal mode. This is impressive.

https://www.youtube.com/watch?v=9YGvfLjje_s

Does it support all the phones? Yes it does but some phones will have limited functionality due to missing sensors, ambient sensors in particular. So phones like the Lumia 630, Lumia 635, and Lumia 530 will have limited functionality.

Thanks Kuldeep | Source