Weeping angel:
Funky asshole alien assassins that turns into stone when someone is looking at them (actually quantum locked but lets leave it at that).

If you stop looking at them or even blink, they go into kill-yo-ass-dead mode and (in earlier episodes) send you back in time so you die of old age, or (in 11th doctor episode) snap your neck and use the dead to make you feel bad via walkie talkie

What doesn't make sense with this picture is: Toph is blind and the angels are impossibly fast... meh guess someone is looking at em offscreen

Now I ain't no fancy Doctor Who fan 'er nothin'. But Toph "sees" by feeling the vibrations in the Earth. Maybe that counts in the WHOniverse. Also, has anyone ever used the term "WHOniverse before? Because if not, I want credit...

They are the weeping angels...
They are incredibly fast and moves up on you even if you as much as blinks. They kill in the most humane fashion known in the show (i think the Doctor says that). When they touch you, they send you back in time so you can live your days out in the past, while they feed on the potential energi from what your life would have been if you had stayed in the present.

(sorry if that didn't make sense, english isn't my first language)

i can't give you all the details (I never watched Dr. Who) but those statues are called like weeping angels or something. They move when you're not looking, and I think they're evil spirits to some extent.

Like I said i don't really know though. I only know they move when you're not looking. Hopefully someone else will come along and explain it.