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.
For example, I regularly plug a Micro USB cable into an iPhone charger and charge with that. Cheap, non phone chargers however, may not be regulated, and that could damage your phone. In short: Any cable or charger from an old phone is fine to use if its Micro USB (same connector).