I use TextMe ... I like it because I can text or call, and it is passcode protected, so no one can access the app without my code. They have a free version, but I ended up paying for it because I was tired of the ads.
Also, I highly suggest the Cake Browser app, you can lock this app as well, and it uses facial or fingerprint to open it. I prefer this over my default browser because all my search history stays safe. And I don't have to worry about the kids or wife seeing my sites when they use my phone.