You’re not going to exactly want to replace your tape measure, but as far as iPhone hacks go, this is about as cool as it gets: Acoustic Ruler allows you to measure distance up to 82 feet using a blast of pure sound.
Here’s how it works. To measure anything, you need either two iPhones running Acoustic Ruler or a wired mic. If you have two iPhones, you just load up the app in both of them, move the two iPhones apart, and set one to be the emitter and the other receptor. The emitter iPhone will then send out a sonic blast, which the receptor iPhone will then convert into distance according to how long the sonic blast took to reach it, adjusting for variables like air temperature.
Don’t have two iPhones? The app will still work as long as you have a wired mic handy, like the one in your iPhone earbuds. Sure, it will only be able to measure the distance between the end of your earbud cable and your iPhone’s speakers, but that would still make for a pretty impressive parlor trick. “How wide is that nickel? Easy. Let me just pull out my iPhone and hit it with a sonic measuring blast!”
Acoustic Ruler Pro is available now on the App Store for just 99 cents.