While video-on-demand still takes up the lion's share of Internet traffic, we are witnessing a significant increase in the adoption of mobile applications defined by tight bit rate and latency requirements (e.g., augmented/virtual reality). Supporting such applications over a mobile network is very challenging due to the unsteady nature of the network and the long distance between the users and the application back-end, which usually sits in the cloud. To address these and other challenges, like security, reliability, and scalability, a new paradigm termed multi-access edge computing (MEC) has emerged. MEC places computational resources closer to the end users, thus reducing the overall end-to-end latency and the utilization of the network backhaul. However, to adapt to the volatile nature of a mobile network, MEC applications need real-time information about the status of the radio channel. The ETSI-defined radio network information service (RNIS) is in charge of providing MEC applications with up-to-date information about the radio network. In this article, we first discuss three use cases that can benefit from the RNIS (collision avoidance, media streaming, and Industrial Internet of Things). Then we analyze the requirements and challenges underpinning the design of a scalable RNIS platform, and report on a prototype implementation and its evaluation. Finally, we provide a roadmap of future research challenges.