Your Cell Phone Can Be Remote Bug, Even When "OFF"
I did not believe it until I found verification. Our government can and has used ONSTAR systems and cell phones to remotely listen in on conversations. As far as we know, they have always gotten a warrant, and the people were the kind where there was indeed probable cause. Still, it is scary to think that even if you have powered down your cell phone and closed it up, it can be remotely turned back on and listening in on you.
Combine this with word recognition software and enough processing power, and you could have something similar to the "Carnivore" program on cell phones. In Carnivore, the government routinely scanned the emails of random people for key words like "explosive".
Even if our government does not use our cells to listen in on us themselves, rumors abound that intelligence services do reciprocal spying on citizens of other countries. They then share data in order to get around democratic safeguards. I can see the say coming where such random bugging of citizens to listen for anti-government key words is technically feasible. The "Can we?" has always been a bigger limiting factor than the "Should we?". Mankind has shown himself unable to resist doing whatever he is able to do.
For details of the technology and how it has been used, click.