  We present work in progress to craft open-sourced numerical tools that will
enable the calculation of electromagnetic counterparts to gravitational
waveforms: the {\tt GiRaFFE} (General Relativistic Force-Free Electrodynamics)
code. {\tt GiRaFFE} numerically solves the general relativistic
magnetohydrodynamics system of equations in the force-free limit, to model the
magnetospheres surrounding compact binaries, in order (1) to characterize the
nonlinear interaction between the source and its surrounding magnetosphere, and
(2) to evaluate the electromagnetic counterparts of gravitational waves,
including the production of collimated jets. We apply this code to various
configurations of spinning black holes immersed in external magnetic field, in
order to both test our implementation, and to explore the effect of strong
gravitational field, high spins and of misalignment between the magnetic field
lines an black hole spin, on the electromagnetic output and the collimation of
Poynting jets.
  We will extend our work to collisions of black holes immersed in external
magnetic field, which are prime candidates for coincident detection in both
gravitational and electromagnetic spectra.
