Put a twist to the story. Take these zombiebots and add a dash of AI. Imagine the horror if they decide we are the enemy.
Nanotech has so many possibilities, health related mostly, but let's take it a step outside the box. Nanobots in your brain will give you the ability to communicate "telepathically" to other people with the same bots in their heads.
I love the concept of nanobots since I was a kid. The whole idea is brilliant. The only downside...and there will be a downside....is that someone will use it for evil, if you will. Or they will become sentient and go on a rampage.
Grey Goo FTW!!!