Can I remotely track someone else's iPhone?
Sure, it's easy with Find My iPhone or the Find Friends app. Of course you need their iCloud password and/or permission to use these.
If you mean, illegally, without the person's knowledge, it's not impossible, but very difficult.
Just need to spy the location if possible the message
Location is easy, if you both have iPhones. From your contact in his phone, select "Share My Location." Then go to your phone, to iMessage, then hit the "i" in the top right corner. Location will be listed, if available.
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