The University of Hawaii Sea Level Center has been collecting, processing and distributing in-situ sea level data for major scientific projects for over 25 years. Experiments supported include NORPAX, TOGA, WOCE, and CLIVAR. Recently, the Center has upgraded the technology used to observe sea level including the installation of Co-located GPS units for the measurement of absolute sea level. The instrumentation used to produce the real-time and near real-time data are reviewed, and advantages of using various configurations detailed and discussed, with conclusions drawn concerning the design of future global sea level monitoring systems.