San Francisco,  An Apple Watch has reportedly been credited with spotting a 12-year-old girl's rare cancer before she was even aware of it, with the help of its heart rate notifications feature.

As reported by Hour Detroit, Imani Miles and her mother Jessica Kitchen now view the Apple Watch as more than just a gadget.

Imani's mother, Jessica, noticed that her daughter's Apple Watch started beeping constantly, alerting Imani to an abnormally high heart rate.

"That's really weird because it's never happened before. It just kept going off," said the mother.

The concerned mother took her daughter to the hospital, where doctors noticed a tumour in her appendix.

It was then that they learned of a "neuroendocrine tumour" on her appendix, which according to doctors, is "rarely seen in children", the report added.

When doctors found Imani's tumour, it had already spread to other parts of her body, requiring her to undergo surgery to remove it.

"If the watch didn't go off, I probably would have just waited and taken her in the next couple of days," Kitchen was quoted as saying.

"If she didn't have that watch, it could have been so much worse," she added.

Imani had surgery at C.S. Mott Children's Hospital in the US to remove the remaining tumour, according to the report.

Earlier this month, Apple Watch detected a 34-year-old woman's pregnancy.

The woman on Reddit posted that the watch indicated that her average resting heart rate had significantly increased in just a few days, which made her suspect that something was off.

In July, a woman's heart was detected with a rare tumour after she received multiple alerts that her heart was in atrial fibrillation.