[en] The development of different detectors based on GEM technology, mainly to be used for beam diagnostic, is described. The use of GEM foils for detector construction started in Frascati on 2002 with the R and D for LHCb Muon Chambers placed at small angle. Ever since several triple GEM chambers have been built for different applications. The results obtained in several beam tests have shown high performances: high rate capability (>50MHz/cm²), good time resolution (∼4ns), good space resolution O(200μm), and good aging resistance after 2C/cm² of integrated charge. Recent developments on readout electronics and power supply for portable detectors are presented.