Monitoring and characterization of channeled beams in high-energy accelerators ideally requires radiation-hard in-vacuum detectors. For this purpose the Cherenkov detector for proton flux measurement (CpFM) was designed and developed by the UA9 experiment, which investigates channeling processes and applications at CERN-SPS. The CpFM is based on thin fused silica bars in the beam pipe vacuum, which intercept charged particles and generate Cherenkov light. Two detectors are currently operational in the SPS accelerator. I introduce the CpFM concept and discuss its applications in crystal-assisted collimation and extraction experiments at the SPS, including results from the most important case studies. A new CpFM development for high-intensity continuous beam monitoring is also presented. Thanks to a solid, simple layout and intrinsically ultra-fast detection, the CpFM concept has been recently used to study the time structures and the delivered intensity fluctuations of the SPS spill, which supplies the fixed-target experimental area of CERN and is expected to supply the proposed beam dump facility for the SHIP experiment.