What app can I use for gps tracking?

I want to track my husband's locations cuz I think he's cheating. All the apps I look at tell me he needs the app on his phone too but he doesn't have an android or iphone. So what app can I use to secretly track his location of his phone? One that works and preferably cheap or free.

You can't.

If you could track anyone's phone for free and without them knowing it then anyone would be able to track yours or anyone else's phone.

Do you really think that would be a very good idea is someone could say track a child's phone without anyone else knowing they were doing it?