  In addition to the next generation of beam-based neutrino experiments and
their associated detectors, a number of intense, low-energy neutrino production
sources from decays at rest will be in operation. In this work, we explore the
physics opportunities with decay-at-rest neutrinos for complementary
measurements of oscillation parameters at long baselines. The J-PARC Spallation
Neutron Source, for example, will generate neutrinos from a variety of
decay-at-rest (DAR) processes, specifically those of pions, muons, and kaons.
Other proposed sources will produce large numbers of stopped pions and muons.
We demonstrate the ability of the upcoming Hyper-Kamiokande experiment to
detect the monochromatic kaon decay-at-rest neutrinos from J-PARC after they
have travelled several hundred kilometers and undergone oscillations. This
measurement will serve as a valuable cross-check in constraining our
understanding of neutrino oscillations in a new regime of neutrino energy and
baseline length. We also study the expected event rates from pion and muon DAR
neutrinos in liquid Argon and water detectors and their sensitivities to to the
CP violating phase $\delta_\mathrm{CP}$.
