Sonobuoys are used by the U.S. Navy to detect and track submarines, ships and other motorized vessels, however they are also very effective for remotely monitoring sounds produced by marine mammals. Sonobuoys are typically deployed from an airplane or boat and are monitored remotely using a VHF radio receiver. This allows great operational flexibility because it is not necessary to remain in the immediate vicinity of the sonobuoy to monitor sounds. Bio-Waves, Inc. has helped The U.S. Coast Guard design and test a portable sonobuoy system to help monitor and mitigate potential impacts to marine mammals during their at-sea training around the main Hawaiian Islands. In another unrelated project for the U.S. Navy, we deployed sonobuoys from small airplanes to monitor acoustic behaviors of baleen whales and large odontocetes in real-time while visual observations of marine mammal behaviors were simultaneously being recorded. We have also developed a system used to moor sonobuoys temporarily. We used this system to monitor night-time acoustic behaviors of coastal dolphins in a remote island location in the Northern Mariana Islands. In addition, we are working to improve DIFAR processing methods to allow us to locate animals more efficiently in real-time. Finally, we are developing a small portable system that can be used on any small vessel or airplane to monitor and record marine mammal sounds, as well as track the positions of the animals that are producing those sounds.