Given increasing obesity rates, reduced physical activity and other unhealthy practices, mobile gamification-based health applications have gained momentum in motivating individuals towards behavioral change. The lack of corresponding frameworks enabling the efficient cooperation between health professionals and independent game developers has resulted in a clutter of mHealth apps, which uncoordinately make use of large numbers of motivational techniques, gamification metrics and health data. In this paper, a unified user-centered framework is proposed, running health applications crafted by external developers within a sandbox, and thus mitigating the most concerning privacy and safety issues. It is capable of differentiating between apps on intervention-level granularity and tailoring suggested treatments based on users and their current environment, and aims at maximizing motivational impact in order to sustain and facilitate healthy lifestyles in the long run.