I had no idea there was one.
If "yes", what do you think of it?
If "no", why not?
If you had no idea there was one, and you have a PSN ID, I [i]highly[/i] suggest you download it. It's nigh-perfection. It like having an Xbox Dashboard on your smart phone, for Playstation 4. I wish Xbox had one, honestly.
You can send and receive messages, invites, and friend requests from anywhere you have internet connection. You can also remotely turn on your PS4.