An open letter to Apple from some investors sparked the tech giant to respond by promising new software tools for parents to restrict and monitor their kids' smartphone use. In a report by The Wall Street Journal, Apple states it has plans to create new software features that will make its current parental controls on iPhone and other devices "even more robust."

"We think deeply about how our products are used and the impact they have on users and the people around them,” Apple said in its statement to The Wall Street Journal. "We take this responsibility very seriously and we are committed to meeting and exceeding our customers’ expectations, especially when it comes to protecting kids."

Apple didn't provide details on its planned, improved parental control features, but it did point back to the controls its software has had in place since 2008. The Settings app on every iPhone has a parental control section that allows adults to restrict website access, control in-app purchases, and install or delete apps, among other things.

But those existing settings haven't been enough to quell the worries of the investors who wrote an open letter to Apple last week, expressing concern about the effect smartphones can have on kids who are glued to those devices. The letter's authors, Jana Partners LLC and the California State Teachers’ Retirement System (Calstrs), control about $2 billion of Apple's shares—a relatively small amount considering Apple's $900 billion market value, but clearly enough to grab the company's attention.

The letter urged the iPhone maker to add controls that allow parents to limit a child's smartphone use. The investors also suggest Apple should aid research that studies the impact of excessive smartphone use on kids and mental health.

Apple did not provide a timeline for the release of its updated parental control features.