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.
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There is one for Xbox. It's called Smartglass. There's a 360 and Xbone version. And I have the PS4 one, but I haven't used it.