If your employer provides you with a cell phone for company use then he can install whatever apps he likes on it.
Have you checked the terms of your contract of employment? It may be that you signed up for this tracking and other monitoring devices/methods when you accepted your contract of employment.
Does your employer give you and other employees company cell phones with GPS tracking to monitor your location at all times during work hours? My boss does. Most of the time, I am doing the outside jobs. Yesterday, I finished my job ahead of schedule and then went to my friend's company for personal things. This morning, I was given a warning that I was goofing around during work.
A HR colleague told me that the boss can not only monitor our location, he a server that collects information on our cell phones, like text messages, phone calls as well as Internet use. What a terrible thing! How could it is possible? Has my boss gone too far if that is true?