Wireless IoT is a promising area in which large quantities of data and information are collected, exchanged, and stored constantly. While these data and information are utilized for good purposes in wireless IoT, great risks arise in that attackers are seeking to exploit the merits of this new technology for their own benefits. In such a resource-constrained environment, devices are easily exposed to various attacks. Confidential private information is as valuable as it is vulnerable. It is difficult for end users to trust wireless IoT and to adopt related applications due to the lack of satisfactory privacy-preserving mechanisms, which has become the major obstacle for the adoption and popularization of wireless IoT. In this article, we first introduce the classical application scenarios of wireless IoT, along with related security and privacy attack models. We then present a brief overview of privacy-preserving schemes of wireless IoT. Based on the classification of application scenarios, we further present recent advances in privacy-preserving mechanisms in wireless IoT. Finally, we discuss open issues and future research directions for these application scenarios in wireless IoT.