Lifesaver is a technique used by the NSA to image computer hard drives. I'm not sure how the program got the name Lifesaver, but there are a couple of interesting things that come up if you google the word. There's a data recovery product called EASIS Data Recovery that was formerly called LifeSaver, and it's possible that the NSA software was developed from this commercial product. Or more cynically, if you google the words lifesaver, image and hard drive you get testimonials from customers of various commercial data recovery tools speaking about the products as being "lifesavers" for their serious hard drive problems. It's easy for me to imagine a bunch of NSA geeks thinking it would be funny to name their hard drive spy software lifesaver.
I thought it would be funny to toss the NSA a lifesaver from the Titanic. The agency must have a sinking feeling right about now, as the Snowden revelations continue to ripple out into the world.