These stations, run by the National Oceanic and Atmospheric Administration (NOAA), are of particular interest right now due to the recent 8.9 earthquake and subsequent tsunami in Japan.
Presently there are 39 stations:
Pressure, temperature and estimated sea surface height readings are collected every 15 seconds. On the map at this link you can click on each station and get live accurate readings.
I hope no other countries have to experience what Japan is going through right now.