Latest research: http://www.pewinternet.org/Reports/2012/Mobile-Health.aspx
Pew's report found that the percentage of mobile phone owners who use their phone to look up health information has increased from 17% in 2010 to 31% this year. However, the report also found that the percentage of mobile phone owners who said they have a health-related application on their phone has remained steady at about 10% since 2010.
According to Fox, some of the most popular health-related apps include those focused on fitness, weight and nutrition
Read more: http://www.ihealthbeat.org/special-reports/2012/susannah-fox-of-pew-research-center-talks-about-new-findings-on-mobile-health-usage.aspx#ixzz2EqEvMM7r