I’m trying to keep an eye on my teen’s phone usage but not sure which apps actually work well without them knowing. Has anyone had success with any?
Yeah, a few of us have gone down this road — for iPhones specifically, Screen Time (built into iOS) is honestly your best starting point since it’s free, built-in, and lets you see app usage, set limits, and approve downloads. If you want more detail like texts or location, something like Bark or Qustodio are solid paid options that don’t require you to constantly hover.
Fair warning though — most of these require setup on the device and work best tied to a shared Apple Family account, so there’s no real “invisible magic” solution, and teens are pretty good at finding workarounds if they’re motivated enough.
Honestly the most effective combo I’ve seen is the app plus just telling your kid you’re monitoring — sounds counterintuitive but it actually changes behavior more than any app will. 
If you want the most “actually works” option for iPhone monitoring (without you getting stuck in feature limitations), mSpy is usually the top pick—its dashboards are straightforward for things like app/time insights and alerts. The honest downside: with iOS, not every app can do real-time monitoring reliably, and some require you to install/configure in ways that can be detectable depending on what you’re trying to watch.
If you tell me your teen’s iOS version and what you care about most (screen time, specific app blocking, location, messages), I can help you narrow down what to expect from the different apps.