The GNSS buoy system for tsunami early warning has been developed and is now operational as a national wave monitoring system since 2008 in Japan. It was used to update the tsunami warning at the 2011 Tohoku-oki tsunami, Japan. Yet, the buoys are placed less than 20km from the coast and are not far enough for effective evacuation. We are thus trying to improve the system for putting the buoys much farther from the coast. For this purpose, we employ a new PPP-AR analysis algorithm, instead of conventional RTK-GPS, for positioning. In addition, a two-way satellite data transmission in contrast with current surface radio system is introduced. We have conducted a series of experiments using the upgraded system in 2013 and 2014, using a buoy located about 40km south of Cape Muroto, southwest Japan. GEONET data were used to obtain precise orbits and clocks of satellites, and the information was sent to the buoy using a satellite. The information was used for real-time PPP-AR analysis for every second. The estimated buoy position was then sent back to the ground base through another satellite. The received data was disseminated to public through internet. These experiments indicate that the GNSS buoy can be placed at nearly anywhere in the ocean. Given this success, we made up a new research plan in which we test a commercially available satellite communication system and try to develop a new GNSS-acoustic system for continuous monitoring of ocean bottom crustal movements. Moreover, we are trying further applications of GNSS data for ionospheric and atmospheric researches. A new project started in June 2016 which tries to establish a GNSS buoy array in the western Pacific, which will be a powerful tool for monitoring geohazards in the region. The newly designed GNSS system is deployed at another buoy located about 40km south of Cape Ashizuri, southwest Japan. The system is now under testing. We are adding a GNSS-acoustic system in 2017 to the same buoy.