It's a little inefficient, but you could use a modified version of this script, which I use to tell me when internet outages finish:
[php]
on idle
set availText to "Your Network Connection is now available."
set secondsToWaitBetweenChecks to 120 -- 2 Minutes between checks
set hostToCheck to "www.apple.com"
set checkNetScript to "curl " & hostToCheck
try
do shell script checkNetScript
say availText
display dialog availText
on error
-- say "DSL still down."
end try
return secondsToWaitBetweenChecks
end idle
[/php]
- you have to save the script as an application.