The Day the Earth Stopped (US-2008; dir. C. Thomas Howell)
Hundreds of massive intergalactic robots appear in all of the major world capitals with an ultimatum: Prove the value of human civilization or be destroyed.
Nice big robots!
And as if that isn't enough, here's one that's coming up which doesn't "shadow" a current blockbuster so much as exploit certain individuals' obsessive fascination for sharks and giant octopi:
Mega Shark vs Giant Octopus (US-2009; dir. Ace Hannah)
The California coast is terrorized by two enormous prehistoric sea creatures as they battle each other for supremacy of the sea.
- Source: Asylum website