There's no shortage of weather apps that'll give you local temperature and forecast information, but let's face it: they're not exactly infallible. Wouldn't it be neat if you could just whip out your iPhone, and not have to hunt down an actual old-fashioned thermometer?
It turns out you can, at least in theory. No current iOS device boasts temperature sensors, but Thermometer 147 claims to measure ambient air temperature using only the onboard audio hardware. Because sound waves travel faster in warmer air, one need only measure the time it takes a sound to get from speaker to microphone.