> Then, one day, an app developer thought: Wouldn't it be cool if there was an app that would interrupt what the user was doing, play a sound, vibrate the devic

> Then, one day, an app developer thought: Wouldn't it be cool if there was an app that would interrupt what the user was doing, play a sound, vibrate the device, and put up a full-screen dialog, that this all could be activated remotely by any other device by simply typing in a short numeric code When you're actively using your smartphone, phone calls show up as notifications, not full-screen dialogs (which trips up my non-technical relatives, since they don't know how to answer a call through the notification). Given that, it's not that different from what we had on computers with instant message applications like ICQ. In a world without the concept of phone calls, they would be a natural evolution from these instant messengers (and, as I'm sure you remember, ICQ used a short numeric code as the user identity).