Finding The Right Line With Phone Monitoring

A coworker recently told me they were thinking about using a phone monitoring app, and it turned into a longer conversation than I expected, at first it sounded simple, because people usually connect this topic with safety, family rules, or checking that a device is not being misused, but the more we talked, the more it became clear that trust matters just as much as features, I came across uMobix phone monitoring app while reading about different options, but I still feel that any tool like this should be used openly and for a clear reason, not secretly or out of pure suspicion, In families, especially with teens, it probably works better when everyone understands the limits from the start, has anyone here used monitoring tools in a way that actually helped instead of creating more tension?