Apple has acquired Tueo Health, a small start-up that was developing a system to help parents monitor asthma symptoms in sleeping children, according to a person familiar with the deal.

It's unclear how much Apple paid for Tueo Health. The start-up raised a small seed round of $1.1 million in funding in 2017. Tueo's CEO and co-founder Bronwyn Harris and chief operating officer Anura Patil changed their employer to Apple on their LinkedIn profiles in late 2018, which is likely around the time Apple completed its acquisition of the company.

An Apple spokesperson declined to comment.

Tueo Health was developing a mobile app that worked with commercial breathing sensors to help manage asthma symptoms in children. The app would send alerts to parents if their child's breathing changed at night.

Apple has been adding more health features across its products, especially the Apple Watch. The latest version of the Apple Watch can perform an electrocardiogram and detect when a user falls, for example.

Apple is also expected to revamp its Health app for iPhones with new features such as tracking menstrual cycles as part of its iOS 13 update, according to Bloomberg. Apple is expected to announce its new iOS 13 features at its annual developers conference on June 3.