If your friend's phone is off, the message "Is your phone on?" will be delivered the next time they open the app."You should not have to turn something off and then back on again to know that it is on. I want to know that my phone is on, reliably and safely, without all the fuss," Tavet Gillson, ON?'s lead creative director, said.

With the app, you can also find out which of your friends' phones are turned on and share the results with your social media friends.