Free group messaging. It's like a private chat room for your small group. Have as many as you want, and it's always free. Now, you can coordinate with coworkers, organize a game night, and keep in touch with family all in the same place.
Contrary to what you might think (or have been told), leaving your phone or laptop plugged in all the time is not bad for its battery. That's because your gadgets, the batteries in them, and the chargers you attach them to are actually pretty smart about the way they do business.
What I would recommend though, is not charging your phone every day. Let the battery wear down. Buy a car charger so that you can charge it while driving if it needs to be. This will save you from buying a new battery every 9-12 months.