  We show that the decay mode B -> D tau nu is competitive with and
complementary to B -> tau nu in the search for charged-Higgs effects. Updating
the relevant form factors, we find that the differential distribution in the
decay chain B -> D nu tau[-> pi nu] excellently discriminates between
Standard-Model and charged-Higgs contributions. By measuring the D and pi
energies and the angle between the D and pi three-momenta one can determine the
effective charged-Higgs coupling including a possible CP-violating phase.
