During the last experimental campaigns at JET, one of the main conclusions was that the control of the pressure alone was not sufficient to sustain high performance regimes in steady state and active control of the safety factor profile was also required. In this paper we present the recent implementation at JET of a real-time system to calculate the electron density and the safety factor profiles directly from the line-integrated density and the calibrated Faraday angle measurements. Current density, electron temperature and density profile are now available in real time using magnetic, interfero-polarimeter and electron cyclotron emission data, thus allowing real-time feedback control of these profiles with the heating and current drive actuators available at JET. We present the description of the algorithms, the hardware and software architecture and the first results.