Continuously measured quantum systems are characterized by an output current, in the form of a stochastic correlated time series which conveys crucial information about the underlying quantum systems. The many tools used to describe current fluctuations are scattered through different communities: quantum opticians often used stochastic master equations, while condensed matter physicists might use Full Counting Statistics.  These, however, are simply different sides to the same coin.  In this talk I will present a unified toolbox for describing current fluctuations. This not only provides novel insights, by bringing together different fields in physics, but also yields various analytical and numerical tools for computing these quantities in practice. Throughout this talk, I will illustrate these results with various pedagogical examples.