Diamond Scale is what looks like a kind of fake novelty app which purports to turn you iDevice into a scale. The best thing is to just describe it to you.
You take your iPhone and place it on an inflated plastic bag (I used a ziplok). Then you tap the “calibrate” button and wait. Then, when instructed to do so, you pale a coin in the center of the top or bottom non-screen section (on top of the home button for instance). Wait again. Finally, you can place an object on top of the coin and wait. The readout move and tells you its weight.
Does it work? Kinda.
I was skeptical, so I paid my $1 and bought the (Universal) app. It uses the device’s gyroscope to minutely track movement, which explains all the waiting around for calibration.
To my surprise, it’s not snake oil: The scale does actually weigh things, with the result in ounces shown on an old-fashioned dial readout (with grams on a digital display). The problem is accuracy. I weighed two objects on my iPhone, and then on my kitchen scale (digital, one-gram accuracy). Diamond Scale said a camera battery weighed 23 grams, and my kitchen scale said 32 grams. I also tried a seashell and it was similarly wrong.
Still, you can’t fault the cleverness behind the app, although the name and the icon (girls; diamonds; fast cars) clearly make this look like a dumb fake. If you’re happy to spend $1 to amuse yourself for a few minutes, then go grab it. Otherwise skip it – it won’t be an accurate way to weigh your coffee beans when on vacation, nor the diamonds and cocaine you regularly measure for your day job.