I'm thinking of tracking my significant others's phone.
Why would you do that?
I think he is cheating on me.
You need to be more trusting. It's going to be bad for both of you to snoop and track their phone.
I have proof that he is doing something wrong.
If you have proof then you should speak to him about it. The proof you may have could be a misunderstanding and it would look bad if you were wrong to snoop.