Plus if you're paranoid enough to use that then frankly you're too paranoid to own a cellphone at all. They can still use it to track your location and to remotely turn on the microphone and eavesdrop on the background sounds.
Given than you are aware of such risks and still has the need to communicate, your next best options is to encrypt your conversations through non-smart phones, and that's where my project, JackPair, can be helpful.
And yes, I'm trying to promote the awareness of my project JackPair, and the technologies behind it. In fact, I'm running a kickstarter campaign now for JackPair (http://bit.ly/jkpair). I think its relevant here because people need to be more aware that they don't really own their smart phone these days.
That said, a law that explicitly gives the state authority to shut down all cell phones in a situation "they perceive" as a risk is an order of magnitude worse.
(The "kill switch" counterpart to JackPair would be systems like mesh networks, ham radio / APRS, etc. GoTenna is one recent commercial product: http://gotenna.com/ Of course it can probably be easily jammed)
"JackPair: protect your voice phone calls from wiretapping by Jeffrey Chang & the AWIT team"
> my voice encryption project