[gregmac]

What? Yes they do. In fact, that's the original purpose of the "phone" part.

I spent 5 seconds searching and found dozens of apps that allow you to remotely enable the microphone on a cell phone (granted, you have to install the app first, though that can also be done remotely).

[Xylakant]

The original purpose of my cell phone is that a present party can either actively initiate or accept a call, allowing a remote party to hear their words. None of these actions is hidden or disguised or can usually be enabled without my consent. Installing a software that would allow a non-present party to initiate a hidden listening connection would be illegal. Yes, such apps are available, just as the smart watches now banned were available.

Note that devices that are obviously and primarily made for recording or transmission are not affected, microphones, video cameras etc. are not illegal.