Manufacturers have been pushing proprietary apps to the Play Store for a while now, because it allows for faster and easier updating of apps without needing to go through the over-the-air process for updates, which users can choose to ignore. Updates through the Play Store are much easier to automate. The latest app to come to the Play Store is Samsung's S Note app.
The S Note app is on most Samsung devices, but is one of Samsung's star apps for the Galaxy Note series because of its use of the S Pen. Users can pull out the S Pen to draw something, jot down a note, or annotate a picture or screenshot. The S Note app in the Play Store doesn't seem to have anything especially new compared to what Galaxy users are used to though.
The app is still rolling out, but it should eventually be compatible with most Samsung devices. The listing confirms that the app will work on Samsung devices that don't use the S Pen, but functionality that requires the S Pen will be missing on those devices.
Interestingly though, users with non-Samsung devices have reported being able to install the app with mixed results. A user in Switzerland with an HTC 10
claims to have successfully installed the S Note app. Someone with an LG G4 could install it, but the app would force close without opening.
It's unclear if this means anything though. Maybe Samsung didn't lock down the app properly and support for non-Samsung devices will eventually disappear. But, it could be that Samsung is actually planning to extend support for the app to non-Samsung devices. The latter may seem unlikely, but maybe Samsung wants users to try the app, see that there are cool things to be done if only they had an S Pen and switch to a Galaxy Note? Stranger things have happened.