The new health- and fitness-tracking platform has been stalled by a software bug. HealthKit was supposed to be a key component of the iOS 8 mobile software update Apple released Wednesday.

Third-party apps built to work with the platform have been pulled temporarily from Apple's App Store as a result.

"We're working quickly to have the bug fixed in a software update and have HealthKit apps available by the end of the month," an Apple (AAPL, Tech30) spokeswoman said.

HealthKit works with Apple's new Health app along with third-party apps like WebMD and MyFitnessPal. It lets users monitor things like heart rate, sleep, weight and blood pressure, and you can also choose to share the information with your doctor.