There are a few tools worth knowing about if you are looking at the monitor child text messages use case specifically. I have tested or researched most of these at some point.
Google Family Link
This is free and built into Android. It does not show full message content but gives you app usage, screen time, location, and the ability to approve or block app downloads. Good starting point before you go to paid tools.
Limitation: Does not read SMS or WhatsApp. Also, once your kid hits 13 they can request to unlink it.
Bark
Works by scanning messages for red flag content like bullying, substance mentions, or self-harm language, then sending you an alert. You do not see every message, just flagged ones.
Limitation: You are trusting their algorithm to catch what matters. Some parents find that too hands-off.
Qustodio
More full-featured. Covers calls, texts, app blocking, web filtering, and location. Works on Android and iOS.
Limitation: The full messaging visibility requires the premium plan which runs around $55 a year. Also on newer Android versions some features require additional permissions that are not obvious to grant.
mSpy
One of the older names in this space. Does show SMS and some social app messages.
Limitation: Mixed reviews on customer support. Some users report billing issues when canceling.
FamiSafe by Wondershare
Good UI, solid location tracking, decent text monitoring.
Limitation: Social media message reading is limited on non-rooted devices.
Most of these work best when the child knows monitoring is in place. The consent model is not just ethical, it is also practically more effective.