Yeah! There are many spy apps available to get installed on the phone which you are targeting to track. But many of them will be visible and they will give the hints to the person who uses the phone. A spy app which is available to download on the website https://www.netspy.net can work as an undetectable. It won't let phone users know that the app has been installed on their phone. It's highly undetectable and designed very smartly. Don’t hesitate to comment on this answer if you need anything else on spying apps to track the other mobile phones.