  Employing the SU(2) isospin symmetry of strong interactions and estimates
borrowed from effective field theory, we explore the impact of new physics on
the decays $B^\pm\to \phi K^\pm$ and $B_d\to \phi K_S$ in a model-independent
manner. To this end, we introduce - in addition to the usual mixing-induced CP
asymmetry in $B_d\to \phi K_S$ - a set of three observables, which may not only
provide smoking-gun signals for new-physics contributions to different isospin
channels, but also valuable insights into hadron dynamics. Imposing dynamical
hierarchies of amplitudes, we discuss various patterns of these observables,
including also scenarios with small and large rescattering processes. Whereas
the $B\to\phi K$ system provides, in general, a powerful tool to search for
indications of new physics, there is also an unfortunate case, where such
effects cannot be distinguished from those of the Standard Model.
