Courtney Cheng's smartphone reminds her when it's time to meditate.

Cheng, 25, a nonprofit project manager in the San Francisco Bay Area, is a paying member of Headspace, one of a handful of apps focused on meditation and wellness that have accrued millions of users — and millions of dollars in venture capital investments. She said she found the app after dealing with a "post-grad crisis" after college. Now, it helps her relax and fall asleep.

But like the many other smartphone notifications Cheng receives throughout the day, she isn't always in the mood to hear from Headspace.

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"I set a reminder on Headspace to send me a notification to remember to use it," Cheng said. "But it makes me laugh because sometimes I'm like, 'I don't want to pick up my phone right now.'"

Smartphones have trickled into almost every part of modern existence, and meditation and wellness are no exception. Device use is so common, detox programs are now popular — and the average person receives 65 to 80 notifications a day, according to research from Duke University. The paradox that even meditation apps may be the cause of anxiety has not stopped millions from turning to devices for relief, making it a lucrative new market in the app economy.

"It does seem silly that it's just another thing to do on my phone," said Sarah Gordon, 25, a project coordinator at Cincinnati Children's Hospital, who pays for Headspace and uses it almost every day. "Even though I don't touch my phone while using the app, the second I open my eyes, I notice myself go to grab my phone."

Users like Cheng and Gordon have contributed to the growth of this new market, proving consumers are willing to pay for apps that provide some mental relief. Cheng pays "just under $100 a year" for the apps, a price she says is worth it. Calm, another popular meditation and sleep app, charges about $70 for a year.

That success has been met with sizable investments from venture capital firms. Headspace has raised $75 million from investors, while Calm recently topped that, raising $88 million and being valued at around $1 billion.

The rise of these apps has coincided with growing concern among consumer advocates, wellness gurus and even big tech companies about smartphone addiction. Michael Acton Smith, co-founder and co-CEO of Calm, said that smartphones can still be a force for good.

"The mobile phone gets a lot of bad press, but if you use it correctly, it's an incredibly positive thing in our lives," Acton Smith said.