In the USA, the Coast Guard has recently updated their radio
watch system to a 21st-century technology system called RESCUE
21. In additional to coastal areas, the system covers the Great Lakes
and many inland river waterways.
For a look at Great Lakes
coverage and details of several RESCUE
sites, please see
continuousWave: Whaler: Reference: Rescue 21 Stations; several sites in Southeast Michigan found and documented
The above article contains photographs and details of several sites and details about the general capabilities of the system and its costs.