Mobile phones have been shown effective in several public health domains. 
However, there are few evaluations of the effectiveness of mobile health in 
health promotion. Also, although many studies have referenced behavioral theory, 
none appears to have explicitly tested theoretical assumptions or demonstrated 
mechanisms of change. More robust evaluation models that incorporate theory and 
measurement of behavioral mediators are needed. As in all public health 
programs, mobile health operates within a social ecological context. For 
example, organizational- and individual-level programs seek to influence health 
and health care practices and individual health behaviors. New programs such as 
Text4baby demonstrate how theory and explicit testing of mediators can be 
incorporated in evaluations. There are challenges and opportunities facing 
mHealth evaluations given the nature of the mobile channel. Mobile communication 
is ubiquitous, available at all times and places, and thus experimental control 
is often difficult. Natural experiments using variation in dosage of mHealth and 
place- or location-based designs may increase experimental control. Text4baby is 
a text messaging program that provides prenatal care messages to pregnant women 
and new mothers. It uses a partnership model with health care facilities often 
serving as local implementation partners. The authors review a case example of 
the evaluation of Text4baby at Madigan Army Medical Center. Participants were 
randomized to usual prenatal care plus text messaging or usual care alone. The 
evaluation has a theoretical model of behavior change and measures mediators as 
well as behavioral outcomes. Results will inform how behavioral theory works 
within mobile health programs.