Mobile phone ringing
Everyone hates it when a mobile phone rings in a cinema, classroom or restaurant. Especially if it's yours.
It's so easy to forget to mute the ringer. It's even easier to forget to turn the ringer back on at the end of the lecture. Turning ringers on and off seems beneath us, and beyond us.
Clearly, it would be better if our phone could decide when to ring for itself. This kind of 'context-awareness' is actually a very hard problem. Here's one simple algorithm that might go a long way towards helping.
If my phone can pick up lots of other mobile phones in close proximity, and they're not moving away, then assume it should be more silent. This covers most of the cases we'd want, where lots of people are sitting together, and no one wants to be disturbed. It excludes cases where we're walking down the street surrounded by lots of other people, but none of us are sticking around.
I can think of a few cases where this might fall down. If I'm anxiously awaiting a call from the hospital about a loved one, I want the phone to ring wherever I am. If I'm sitting in a noisy coffee shop, I want it to ring loudly, and no one will be particularly disturbed.
But on balance, this seems like a good heuristic. Instead of having a manual 'mute' button, we might just let the phone guess, and have a manual 'loud override' button for the above cases.
The problem is that often, we'd rather our devices be dumb but predictable than smart but surprisingly and unpredictably tricksy.