Can you turn an iPhone 6S into a working digital scale? The answer, apparently, is yes, but Apple doesn't want you to right now.

One of the first problems he and his team faced was that Apple's 3D Touch API measures weight on a custom scale from 0.00 to "maximum possible force," with 1.00 as the average touch. They solved this by asking users to calibrate the app using objects of a known weight they would have to hand (US nickels). Then there was the problem of getting the screen to recognize touch input. "We needed an object that was conductive, had finger-like capacitance, formed a single finger-like touch point, was a household item, and could hold items to be weighed," writes McLeod.

Their solution? A spoon. Users could balance objects on the spoon and get, well, not a completely accurate reading (and nothing heavier than the maximum weight of 385 grams), but something that was far better than no scale at all.

With these problems tackled, the team submitted their Gravity app to the App Store. It was rejected "for having a misleading description," says McLeod, which he puts down to the fact that there are dozens of "digital scale" apps available on iOS, but these are "for entertainment purposes only." The team resubmitted with a video showing the app in action (above), but were then told on the phone that "the concept of a scale app was not appropriate for the App Store."

It's not clear exactly what the reasoning behind this is. The quote above is from McLeod, not Apple, and the company has yet to respond to a request from The Verge for comment. It could be that Apple is worried that people will break their screens if they use them as scales (although this wouldn't explain the availability of joke apps) or that it thinks such an app would be used for weighing drugs (a possibility, although most drug dealers would probably prefer a $20 digital scale that's actually accurate).

Huawei demonstrated their rival Force Touch technology by weighing an orange using the Mate S onstage.

The other answer is that Apple simply doesn't know what it thinks about digital scale apps yet and so is defaulting to "no." The idea is popular, though. Another developer has built a Plum-O-Meter which tells you out of two plums placed on the iPhone's screen, which is heavier. And during the unveiling of Huawei's new Mate S smartphone at IFA this year, the company weighed an orange onstage using their rival Force Touch technology. (In my hands-on with the Mate S, I found that the scale function was imprecise and fickle, but undoubtedly a cool trick to show your friends at the bar.)

"We have a strong respect for the subjective process Apple uses to maintain a selection of high quality apps," writes McLeod on Medium. "But [we] do hope for a day when Gravity can be one of the hand-picked, who-knew-a-phone-could-do-that-apps anyone can download on the App Store and have in their pocket." Let's see if Apple agrees.

Verge Video: This is how 3D Touch works on the new iPhone