Fittingly, the Surface has a pro line-up of cameras and sensors:

Infrared emitter

Infrared camera

Front-facing camera

"Privacy light" indicator LED (mounted on the rear-facing camera)

Microphone

Ambient light sensor

We're pretty sure the lil' guy marked in red is an IR emitter, like the one found in Project Tango. It should work with the IR camera to recognize your face and unlock your computer. Aw, he knows his mummy.