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 21
radio 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.