  Some rare hadronic decays of B mesons, such as B->pi K, are sensitive to
isospin-violating contributions from physics beyond the Standard Model.
Although commonly referred to as electroweak penguins, such contributions can
often arise through tree-level exchanges of heavy particles, or through
strong-interaction loop diagrams. The Wilson coefficients of the corresponding
electroweak penguin operators are calculated in a large class of New Physics
models, and in many cases are found not to be suppressed with respect to the
QCD penguin coefficients. Several tests for these effects using observables in
B->pi K decays are discussed, and nontrivial bounds on the couplings of the
various New Physics models are derived.
