  We report on the detection of the millisecond pulsar PSR J0437-4715 with the
Murchison Widefield Array (MWA) at a frequency of 192 MHz. Our observations
show rapid modulations of pulse intensity in time and frequency that arise from
diffractive scintillation effects in the interstellar medium (ISM), as well as
prominent drifts of intensity maxima in the time-frequency plane that arise
from refractive effects. Our analysis suggests that the scattering screen is
located at a distance of $\sim$80-120 pc from the Sun, in disagreement with a
recent claim that the screen is closer ($\sim$10 pc). Comparisons with higher
frequency data from Parkes reveals a dramatic evolution of the pulse profile
with frequency, with the outer conal emission becoming comparable in strength
to that from the core and inner conal regions. As well as demonstrating high
time resolution science capabilities currently possible with the MWA, our
observations underscore the potential to conduct low-frequency investigations
of timing-array millisecond pulsars, which may lead to increased sensitivity
for the detection of nanoHertz gravitational waves via the accurate
characterisation of ISM effects.
