Dark matter annihilation or decay may produce striking signatures in
millimeter, sub-millimeter and radio frequencies — for example, via
electrons that produce synchrotron radiation in galactic/cluster magnetic
fields, heating of the intergalactic medium during the epoch of
reionization, or distortions to the spectrum of the cosmic microwave
background. The small-scale structure of dark matter may be probed by
improved lensing observations, in turn constraining new physics in the dark
matter sector. Finally, searches for dark matter signatures at all
wavelengths are complicated by astrophysical backgrounds that
radio/mm/sub-mm searches could help address. I will discuss the current
status and future prospects of these various directions.