Here is a map of APRS stations around the continental US, in
near real time: http://wu2z.rutgers.edu/aprs.html. The green
stars are digipeaters (digital repeaters). As I mentioned
here before, in New Mexico there is nearly state-wide coverage
by digipeaters, so that the standard handheld radios used in
SAR (which have very low power and a frequency that does not
travel far beyond line of sight) can be heard all across the
state.
Una Smith
Santa Fe County Sheriff's Posse, in New Mexico