Using 3D Touch to Create a Digital Scale
Ryan McLeod on his rejected Gravity app:
We’re on the phone talking through this initial hurdle, when my excitement turns to concern. I start recalling other times Apple hasn’t exactly been stoked on novel uses of their devices’ sensors, but then I remember that despite this the App Store is speckled with creative workarounds including a panorama app that uses vibration to rotate the phone, magnetometer-based stud finders, camera/flash-based heart-rate monitors, and even Square’s ubiquitous headphone-jack card reader. A creative solution is waiting to be found. Creating a scale turns from impossible to a challenge.
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Conductive, capacitive, common, and curved to a single-point of contact. A spoon was the perfect solution we had been looking for.
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With the force values linearly correlated to weight, turning any force into a weight was going to be as simple as recording the force of known weights and creating a linear regression. It’d even be possible to use some statistics to predict how well the calibration went (there are many factors that can throw off a calibration). We opted to use coins for calibration, with a framework that made it easy to internationalize in the future.
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To make a long story short the final answer over the phone was that the concept of a scale app was not appropriate for the App Store.
Update (2015-11-05): Dan Moren:
Really, what Apple needs is a small group within the App Store review team to flag apps that are pushing the envelope in smart, respectful ways; work with those apps’ developers; and present overall recommendations to App Store leadership—perhaps even reporting directly to Eddy Cue. Blanket rejections get you nowhere, and they increase the frustration of developers who are legitimately trying to do cool things that delight users—just as Apple aims to do.
