Maybe a combination kinetic shield/cloaking device that can only have one mode on at a time, and each mode has drawbacks, like the kinetic shield protects from bullets, but not punches, and the cloaking device only fully works when not moving.

As for plot integration, we find and kill an alien commando team using cloaking devices/whatever inside the hospital during a full scale attack, steal their cloaking devices/whatever, and flee before getting overrun.

By the way, Rax, what was your first link from?

And @jman221: Don't worry about us, go ace your exams or whatever. We're just brainstorming ideas for you.