The gang over at 9to5mac have pieced the information together from multiple sources supposedly working directly on the app, and have recreated screenshots of the software to boot.
The grabs show that Apple wants to go well beyond just another fitness app: alongside sleep and activity tracking, you'll find places to store your weight, heart rate data, blood pressure, blood sugar, nutrition information, respiratory rate and hydration.
It's unlikely that the iPhone 6 or iWatch, which we expect to launch with iOS 8 and hence the Healthbook app, will have all the necessary smarts to analyse your blood directly. We reckon there'll be a certain amount of filling data in based on what your doctor tells you.
But some elements could be tracked by the iWatch - one rumour we've heard to date claims that the wrist-worn device will be able to study the sounds blood makes as it flows through the veins in your wrist and predict heart attacks on that basis. Sounds far-fetched, sure, but so did having the internet in your pocket back in 2005.
The iPhone 6, meanwhile, is said to be rocking an array of new sensors - indeed, even Tim Cook has said, "The whole sensor field is going to explode. It's a little all over the place right now... with the arc of time it will become clearer."
But there's no confirmation on any of this: even 9to5Mac notes that Healthbook might not launch with iOS 8 or even at all if Apple can't make the sensors work the way it wants. So take the whole shebang with the requisite portion of salt for now.
Check out our concept video of what we really hope the iPhone 6 looks like:
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Former UK News Editor for TechRadar, it was a perpetual challenge among the TechRadar staff to send Kate (Twitter, Google+) a link to something interesting on the internet that she hasn't already seen. As TechRadar's News Editor (UK), she was constantly on the hunt for top news and intriguing stories to feed your gadget lust. Kate now enjoys life as a renowned music critic – her words can be found in the i Paper, Guardian, GQ, Metro, Evening Standard and Time Out, and she's also the author of 'Amy Winehouse', a biography of the soul star.