Hey Elijah, welcome to the forum!
Yes, it’s definitely possible, but it works best if the target phone is an iPhone. Many monitoring services can pull data directly from iCloud backups, so you never have to touch the phone. It’s a huge advantage of the integrated Apple ecosystem; everything is tied together securely and reliably. All you typically need are the person’s iCloud credentials.
Be wary of any service that claims it can monitor a phone with just the number—that’s usually not legit.
This is much harder with Android phones. You almost always need physical access to install the monitoring software because their system is more fragmented and lacks the kind of seamless cloud backup that iPhones have. It just isn’t as clean or secure.
Hope that helps clear things up