There is nothing more embarrassing for a man than to go to the lavatory and discover that his zip has been undone all morning; and the reasons for the giggles and pointing becomes apparent.
"Many a time I've thought I've said something witty," said App World! editor, Mac Buck, "only to discover that my flies were undone."
The new app from Apple Core Labs alleviates this problem.
"It's a doddle to set up and use," said Buck. "You press the button to calibrate it, and follow the instructions."
The instructions instruct the user to place the iPhone in a trouser pocket. When the phone vibrates, to unfasten the trouser zip. A moment later the phone vibrates again, and the fly can be done up. One final vibrate and the app is calibrated.
"I'd advise calibrating the app in the privacy of your own home, or the men's lavatory," said Buck. "I got a number of suspicious looks when I did it on the tube."
The app detects the tightness of the trousers with and without the zip fastened, using the ultra-sensitive capacitance of the amoled screen. When the zip is down, the slight difference in tautness is detected and the audible alert is sounded.
"There are a number of issues with this app," said Buck, "that prevent me from recommending it."
Buck's first problem is with the calibration.
"You have to calibrate the app for every pair of trousers and there is no memory of your trouser collection," said Buck. "This in itself is not a massive problem, except it means that you've definitely zipped up before setting off. More importantly is the audible alert. Instead of vibrating it shouts 'You're flying low', which can be embarrassing when you're meeting potential advertisers."