AccuTracking

Does it need to be installed on my phone or the other phone? Can it track previous messages via text or only those received after installation? What other information would I need to have success of any sort?

Thanks

I'll spare you the long sordid details, but in short, Im trying to locate someone (supposedly) very close to me, but I have very limited information on them, the only legitimate piece being a cell phone number. Yes, I've tried tracing the phone number as well as tracing the IP address of past emails...