Almost all so-called “anonymous” phone-tracking apps are scams or malware—they can’t magically bypass iOS’s privacy layers. Real, legal tracking only happens with the owner’s permission via Apple’s Find My (they must enable location sharing with you) or Google’s Find My Device (they need to be signed into their Google account). iPhones use end-to-end encryption on location data and even notify you when someone adds you, so it’s rock-solid private.
On iOS, the easiest, most reliable workaround is Family Sharing with Find My enabled—just set up geofence alerts and you’ll get real-time notifications when someone arrives or leaves. Android’s open ecosystem does let you fiddle with more third-party tools, but that freedom also makes it a prime target for sketchy, privacy-invading apps.