The protection of users' privacy is an important property of smartphone apps. However, most apps do not honour the privacy of their users. One reason for this deficiency is that developers are unaware of and struggle with the implementation of protection techniques. In this paper, we propose an infrastructure to simplify the use of privacy enhancing technologies (PET) in apps. Furthermore, AppPETs provides incentives for app developers to build privacy-preserving apps. The AppPETs concept consists of a client-side library (P-Lib), a hosting environment for privacy services (P-Services), an anonymous communication network, and an audit process. AppPETs supports various types of anonymity that are relevant for real-world use cases. It closes the gap between research and practice in this field and will foster the adoption of PETs on mobile devices.