The US Government has a tidy selection of apps and mobile-configured websites for your handheld device. Go to: http://www.usa.gov/ and click on the More Mobile Apps button (lower right of the screen). Click on the All Apps link. Apps and mobile-enabled websites include:
MedlinePlus Mobile: a lite version of MedlinePlus.gov available for all mobile devices at: http://m.medlineplus.gov 
BMI Calculator from NHLBI: allows you to easily calculate the body mass index and thus percentage of body fat (only available for the iPhone).
Additional government resources available on all mobile devices include:
AIDSinfo: access information on the latest federally approved HIV/AIDS medical practice guidelines, HIV treatment and prevention clinical trials, and other research information for health care providers, researchers, people affected by HIV/AIDS, and the general public. http://m.aidsinfo.nih.gov/
PubMed/MEDLINE: access the world’s largest biomedical database on the go at http://pubmedhh.nlm.nih.gov/.
You can also find free government health apps in the iTunes store, such as:
AHRQ ePSS: enter in basic demographic and risk factor data and it will list suggested counseling, health screenings, and preventative medication services recommended by the U.S. Preventative Services Task Force. It also provides Internet access to some of the screening and assessment tools.
Health Hotlines: this consumer health resource lists descriptions and toll-free numbers of nearly 9,000 biomedical organizations.