See also anti-derailment application

A couple can access phone calls, text messages, emails, any activity on Facebook, as well as photos and videos.
On July 20, mSpy launched mCouple, a smartphone app that helps users track every detail of their partner's daily life to prevent cheating. Those worried that their husband or wife might cheat can breathe a sigh of relief!
MCouple can access every phone call, text message, email, Skype and any activity on Facebook, as well as photos and videos taken on mobile devices. MCouple users can even record their partner's phone calls, using GPS technology to track their activity.
MSpy stresses that consent must be obtained before downloading mCouple to the couple's phone. The company mainly recommends the app to bosses who need to monitor their children and perhaps their employees' behavior but admits that many customers use mCouple to try to track down cheating partners.
Many lawyers say any covert surveillance is illegal. Jeremy Clarke-Williams, a privacy expert at Slater & Gordon, said: 'in general, if one partner or even the boss installs a similar app on someone else's phone, it should be considered an invasion of privacy.