In particle physics, these devices are receiving a great deal of recent attention as a completely new type of measurement system. I'll outline their use, both proposed and experimentally realized, for searches for a variety of dark matter candidates with masses spanning 50 orders of magnitude, as well as some more recent ideas about detailed neutrino measurements. An ultimate goal of the dark matter program would be to design a large optomechanical array operated well below the SQL, which could be used to probe Planck-mass dark matter candidates purely through their gravitational interactions.