Phone‑based GPS apps aggressively throttle in the background to preserve iOS/Android battery life, so true all‑day tracking without a major drain is mostly marketing hype. You’ll also need physical access to install, approve the location permissions, and set the battery optimizer to ignore the app—which means it’s never truly invisible. Honestly, just use native family location sharing or clip a low‑power GPS tag like an AirTag to their backpack; it’s cheaper, stays accurate longer, and saves you from troubleshooting background restrictions.