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.
The most harmful is overcharging which should be limited by the cell phone. Therefore that's not something the average person can control. The next most deleterious to a battery is cycles of charging - normal battery life is often considered to be about 1000 full charge/discharge cycles. Limiting the discharge/charge cycle to only halfway will double that number of charge/discharge cycles before the battery is considered bad.