A way for non programmers to send push notifications?

[cgl102770]

I'm a web designer who developed an android app for a client with the help of an android developer. Is there an easy way for my client, who knows no code, to send push notifications? I was hoping for a simple app or website where he could load his contacts who've downloaded his app, then create a push message, then choose who among his contacts to send it to? Does such a thing exist? Thank you for any feedback.