A good example is how "Action Launcher" does this.
Basically if you visit Settings, it has a simple text each year.
OR if there is a big major update (see pics), it includes a notice about this thing.
IF you want to support development, you can pay some amount, and you get a cool badge in settings.
So no left out people, no real benefits.
Just a warm fuzzy feeling.
I love AquaMail, it's the only proper client for Android.
Please, add this.
(Yeah, yeah, you get a "live wallpaper", but to be honest no one uses that, we just pay to keep Action Launcher alive.)