The increasing computing power and bandwidth of FPGAs opens new possibilities in the field of real-time processing of HEP data. LHCb has introduced a novel a cluster-finder architecture based on FPGAs, aimed at embedding "on-the-fly" hit reconstruction directly in the readout firmware of the VELO pixel detector. Besides shrinking the high-level trigger workload by providing it with pre-reconstructed data, this system enables further opportunities. Thanks to the triggerless readout architecture of LHCb, these reconstructed hit positions are available for every collision, amounting to a flow of 10$^{11}$ hits per second, that can be exploited for unbiased precision monitoring and diagnostics of LHCb interaction region. In this poster, we describe the design, integration and performance of a set of real-time cluster density counters. These counters provide several independent averaged and per-bunch-crossing measurements of instantaneous luminosity, and average beam spot position; they can also be exploited to study the movements of the VELO detector itself. The counters function without any slowdown of data acquisition and achieve statistical precision comparable with offline measurements.