But Fitbits aren't particularly useful if you're homeless, and the nutrition app won't mean much to someone who struggles to pay for groceries. Same for emailing your doctor if you don't have a doctor or reliable internet access.
"There is a disconnect between the problems of those who need the most help and the tech solutions they are being offered," said Veenu Aulakh, executive director of the Center for Care Innovations, an Oakland-based nonprofit that works to improve health care for underserved patients.
At most digital health "pitchfests," it's pretty much white millennials hawking their technology to potential investors.
"It's about the shiny new object that really is targeted at solving problems for wealthy individuals, the 'quantified-self' people
who already track their health," Aulakh said. "Yet ... What if we could harness the energy of the larger innovation sector for some of these really critical issues facing vulnerable populations in this country?"
A small but growing effort is underway to do just that. It's aimed at using digital technologies -- particularly cellphones -- to improve the health of Americans who live on the margins. They may be poor, homeless or have trouble getting or paying for medical care even when they have insurance.
The initiatives are gaining traction partly because of the growing use of mobile phones, particularly by lower-income people who may have little other access
to the internet.
The Affordable Care Act and the expansion of Medicaid have added millions of previously uninsured people to the nation's health care system, including community health clinics that serve poor and largely minority populations, according to a California Health Care Foundation report
(PDF). (Kaiser Health News publishes California Healthline, an editorially independent publication of the California Health Care Foundation).
In California alone, the number of people on Medi-Cal, the state's version of the Medicaid program for the poor, rose from 7.5 million
(PDF) in 2010 to 12.4 million by early 2015. Many Americans remain uninsured, however, because they live in states that have declined to expand Medicaid eligibility.
Health advocates say it's important to tailor digital health technologies to lower-income people not only to be fair, but because they're more likely to have chronic illnesses, like diabetes, that are expensive to treat.
Health-care providers have incentives as well. They are being rewarded financially under the Affordable Care Act, Medicare and Medicaid for keeping patients healthy, and this goes beyond simply performing medical procedures and prescribing drugs.
For now, experiments targeting low-income people are a tiny part of the digital health industry, which racked up an estimated $4.5 billion
in venture funding in 2015 alone. Entrepreneurs are still trying to figure out how they're going to get paid by serving this population, and government health programs like Medicaid and Medicare are taking a while to figure out
how they're going to pay providers for approaches that don't involve a doctors' visit.
But Jane Sarasohn-Kahn, author of the California Health Care Foundation report, says investors are getting more interested in digital health initiatives for low-income patients simply because there are so many of them.
Investors are eyeing the "fortune at the bottom of the pyramid," she said, much as Walmart profits from selling low-priced items to millions.
"It's now sexy to scale," she says. "If you can have impact [on many people], inexpensively, you can make a lot of money. If we get it right, we can do well and do good."
Some initiatives are simple and cheap, like Text4Baby
. The free text-messaging service for pregnant women and new moms offers English- and Spanish-language information about prenatal care, labor and delivery, breastfeeding, developmental milestones, and immunizations -- all timed to the baby's due date.
Operated by the nonprofit ZERO TO THREE and the mobile health company Voxiva, Inc., Text4Baby has reached nearly 1 million women since starting in 2010. In one survey
(PDF), more than half of them reported yearly incomes of less than $16,000.
Other experiments are far more elaborate. In California and Washington state, San Francisco-based Omada Health
is testing a version of Prevent, a diabetes and heart disease prevention program that's been modified for "underserved" populations -- basically people on Medicaid or who are uninsured. The free program offers patients a digital scale as well as behavior counseling and education, access to a personal health coach and an online peer network.
To adapt the program, the company made it available in Spanish and English and lowered its reading level from 9th grade to 5th grade. Bilingual health coaches were hired, and the educational materials now acknowledge potential food access, neighborhood safety and economic issues that participants may face, said Eliza Gibson, Omada's director of Medicaid and safety-net commercial development.