The app is posted as open source on GitHub (See post #40)
https://github.com/ninthbit/RPoLNotifier
Anyone could download the code, compile it, and sideload it to their phone (assuming they have the rights on their device).
I'm not currently playing in any games and rarely even visit RPOL anymore. As sad as it is, I don't even have my own app installed currently. :(
As for features, You can have unique icons per game. The app pulls your character portrait to use for each game.
For selecting what you're following, it uses your sticky list. Well, actually it uses your ATOM xml feed, but RPOL generates that from your sticky list, so removing games like Community Chat and the like from your sticky list will stop the app from trying to notifiy you.
Many of the apps limitations come from the fact that we're basically scraping the site. I don't have access to the server to setup push notification for things like rMail. I have to have my server poll the site on a set interval, and then push a notice when it sees something.