Companies such as http://flexispy.com/ (external - login to view) allow customers to spy on their partners without their knowledge. They're not the only ones doing it.
From Flexispy's website: Download FlexiSPY spyphone software directly onto a mobile phone and receive copies of SMS, Call Logs, Emails, Locations and listen to conversations within minutes of purchase.
FBI taps cell phone mic as eavesdropping tool http://www.news.com/2100-1029_3-61401... (external - login to view)
Big Brother Is Listening to Your Cell Phone Calls
http://www.truthnews.us/?p=746 (external - login to view)
FBI Can Eavesdrop on You Even When Your Cell Phone is Turned Off
http://axiomsun.com/home/video/fbi_ca... (external - login to view)
Is the government listening? The expansion of domestic spying after 9/11 raises some thorny constitutional issues http://findarticles.com/p/articles/mi... (external - login to view)
Big Brother Was Listening In A Long Time Ago http://www.prisonplanet.com/articles/... (external - login to view)