You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: A Preliminary Survey of Knowledge Discovery on Smartphone Applications (apps): Principles, Techniques and Research Directions for E-health 
Chapter Title:  A. Findings 
1. Abstract of Cited Paper (BIB001):  Background: The introduction of Apple’s iPhone provided a platform for developers to design third-party apps, which greatly expanded the functionality and utility of mobile devices for public health. Objective: This study provides an overview of the developers’ written descriptions of health and fitness apps and appraises each app’s potential for influencing behavior change. Methods: Data for this study came from a content analysis of health and fitness app descriptions available on iTunes during February 2011. The Health Education Curriculum Analysis Tool (HECAT) and the Precede-Proceed Model (PPM) were used as frameworks to guide the coding of 3336 paid apps. Results: Compared to apps with a cost less than US $0.99, apps exceeding US $0.99 were more likely to be scored as intending to promote health or prevent disease (92.55%, 1925/3336 vs 83.59%, 1411/3336; P <.001), to be credible or trustworthy (91.11%, 1895/3336 vs 86.14%, 1454/3349; P <.001), and more likely to be used personally or recommended to a health care client (72.93%, 1517/2644 vs 66.77%, 1127/2644; P <.001). Apps related to healthy eating, physical activity, and personal health and wellness were more common than apps for substance abuse, mental and emotional health, violence prevention and safety, and sexual and reproductive health. Reinforcing apps were less common than predisposing and enabling apps. Only 1.86% (62/3336) of apps included all 3 factors (ie, predisposing, enabling, and reinforcing). Conclusions: Development efforts could target public health behaviors for which few apps currently exist. Furthermore, practitioners should be cautious when promoting the use of apps as it appears most provide health-related information (predisposing) or make attempts at enabling behavior, with almost none including all theoretical factors recommended for behavior change. [J Med Internet Res 2012;14(3):e72] 
2. Abstract of Cited Paper (BIB002):  We report on our extended research on GymSkill, a smartphone system for comprehensive physical exercising support, from sensor data logging, activity recognition to on-top skill assessment, using the phone's built-in sensors. In two iterations, we used principal component breakdown analysis (PCBA) and criteria-based scores for individualized and personalized automated feedback on the phone, with the goal to track training quality and success and give feedback to the user, as well as to engage and motivate regular exercising. Qualitative feedback on the system was collected in a user study, and the system showed good evaluation results in an evaluation against manual expert assessments of video-recorded trainings.

Literature Review:
As can be seen in the survey of the approaches listed in Table I , 8 out the 30 articles selected focus on evaluating diabetes diagnostic-related applications. The second most discussed topic is that dealing with applications offering advice on physical activities, for example, e-coach BIB003 , injury and pain management solutions  BIB001 BIB002 . This reflects a need of our community for advice on personal health challenges. According to statistics cited in AppBrain  , there are more than 28,000 health apps on the Android market. Thus, the result of this analysis represents only a very small proportion of the health apps on the market. In sum, we acknowledge that there should be some methods which can be used to help researchers to discover useful information regarding these apps, and improve the speed of research progression. To that end, researchers can put more focuses on the content of their studies which benefit society. Thus, hereafter, current proposed principles for categorizing medical smart phone apps and reviewing techniques for recommendations of apps and methods of knowledge discovery concerning the smart phone app market are introduced to help us understand the gap between the information available to app users and suppliers.