"As long as that phone is on, you can be tracked and information gathered,
even to turning it on without you knowing so you can be recorded.

“Researchers at Purdue University are working on tech that will turn every cellphone into a roaming nuclear weapon sniffer and are lobbying Congress to legally require cellphone users and carriers to participate. The Distributed Nuclear Detection by Ubiquitous Cellphone project would be kind of like the massive cellphone dragnet in The Dark Knight, but it would look for terrorists sneaking dirty bombs and nuclear weapons instead of the Joker.” - Source