Look, I’ll be straight with you - anything claiming to track WhatsApp activity with just a phone number is probably BS. WhatsApp’s encryption makes that basically impossible without installing something directly on the phone.
Most legit monitoring apps (like the one we’re on the forum for) need to be installed on the device you want to monitor. That’s the whole custody arrangement thing - you need physical access and legal right to monitor.
If you’re seeing ads for “just enter a number!” apps, they’re either scams fishing for your credit card or straight-up illegal spyware. Neither is a good look, especially if things go sideways legally.
What’s your actual situation here? Are you trying to monitor your own kid’s phone or something else?