A way for non programmers to send push notifications?

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.

There are a number of services. I’ve never used any, but I’ve had good experiences with the people from PushIO. They allow what you’re talking about; pushing to apps, android or ios, from a web interface.
The cost should scale pretty cheaply too.

MiniMob (affiliated with Leviteo) also offer a push notifications service which you can use for free. I’m trying them out at the moment.