For an iPhone, start with Apple's own stack — Screen Time, Family Sharing and Find My — because it is free, cannot be broken by an iOS update, and does more than most paid iOS apps can. The paid apps that matter are the ones that solve what Screen Time cannot: content filtering across all browsers and apps, and a proper activity report.
What iOS gives you free, and it is a lot: app limits and downtime, Communication Limits (who can be contacted, per time window), content and privacy restrictions (explicit music, web filtering, app installs, purchases), location via Find My, purchase approval with Ask to Buy, and a weekly report.
Where free stops: Screen Time's web filter is Safari-centric and coarse, there is no message visibility, and the report is per device rather than per person across devices. That is where paid products fit — OurPact, Qustodio, Bark and Apple's own Configurator profiles all target the gaps, mostly web filtering and reporting. Bark adds AI scanning of texts and social content, which is the one genuinely different capability on iOS.
What to avoid: any app claiming to read another iPhone's messages or social chats. iOS does not permit it, so those listings are selling an iCloud backup view or nothing.
Where our app fits, honestly: we have no iOS product. Ultimate Phone Spy runs on Android 4.0+, Windows and macOS (supported devices). For an iPhone family, Screen Time plus one filtering app is the right stack, and it costs far less than a monitoring subscription.