  We combine the concept of Bell measurements, in which two systems are
projected into a maximally entangled state, with the concept of continuous
measurements, which concerns the evolution of a continuously monitored quantum
system. For such time-continuous Bell measurements we derive the corresponding
stochastic Schr\"odinger equations, as well as the unconditional feedback
master equations. Our results apply to a wide range of physical systems, and
are easily adapted to describe an arbitrary number of systems and measurements.
Time-continuous Bell measurements therefore provide a versatile tool for the
control of complex quantum systems and networks. As examples we show show that
(i) two two-level systems can be deterministically entangled via homodyne
detection, tolerating photon loss up to 50%, and (ii) a quantum state of light
can be continuously teleported to a mechanical oscillator, which works under
the same conditions as are required for optomechanical ground state cooling.
