Mobile portable embedded devices are becoming an integral part of our daily activities in the vision of Internet of Things (IoT). Nevertheless, due to lack of mobility support in the IPv6 routing protocol for low-power and lossy networks (RPLs), which is standardized for multihop IoT infrastructures, providing reliable communications in terms of packet delivery ratio (PDR) in mobile IoT applications has become significantly challenging. While several studies tried to enhance the adaptability of RPL to network dynamics, their utilized routing metrics have prevented them from establishing long-lasting reliable paths. Furthermore, the stochastic parent replacement policy in the standard version of RPL has intensified this challenge. Aside from this, due to the existing tradeoff between reliability and power efficiency, most of the existing approaches have only concentrated on one of these concerns without paying attention to the other one. To address these issues, this article introduces ARMOR, a routing mechanism built upon RPL, which employs a novel mobility-aware routing metric, i.e., time to reside (TTR), and a corresponding parent replacement policy. According to the motion characteristics of the mobile objects, TTR provides an estimation of how long the nodes will be in the transmission range of each other. This enables ARMOR to select nodes, which provide longer connection period and consequently higher reliability. In comparison with the state of the art, while keeping the power consumption constant, ARMOR significantly improves the amount of PDR in the network by up to , while it enhances the reliability against the original version of this protocol by up to .