I believe TextNow is only for Apple products, correct? And the other one Kik - all users must download the app in order for it to work, so if only 10 percent of your friends have it won't work? I don't have the apps so cannot speak with great authority here, unlike some posters, but that is how I understand it.
Pre teens, Teens and college kids -- they are texting. Not Instant Messaging, like those other apps are.
Seems like Phoneguard would disable these apps so I don't get your point.