Text message monitoring app for iphone?

No app reads iMessages or SMS on an iPhone. Apple does not expose the Messages database to third-party software, so every "iPhone text monitoring" product you see is doing one of three things: reading an iCloud backup, showing you a notification, or lying. Which one it is decides whether it is worth any money.

The three real mechanisms:

1. iCloud backup parsing — the service holds your Apple ID credentials, decrypts backups, and shows message history on a delay (usually hours). Two-factor authentication alerts the account holder every time, and the backup only contains what synced.
2. Jailbreak — a tweak on a jailbroken phone can read the database. Modern iOS versions make this impractical, and it voids the device's security model.
3. Screen Time — no content, only Communication Limits (who can be reached, when).

What no iPhone product does: live SMS, WhatsApp content, or Snapchat chats. Those claims are the tell that a listing is fake.

Where our app fits, honestly: we do not sell an iPhone product. Ultimate Phone Spy runs on Android 4.0+, Windows and macOS (supported devices), where SMS, MMS and call logs are readable with the app installed and the child informed. If the device is an iPhone, the honest stack is Screen Time plus a shared Apple ID if the child is young.