Is there a Ping Module?
The multiping module will provide this feature in Drupal 7, since the ping module is not part of core anymore. The D7 branch hasn't been started, but there is a patch that you can test that ports the module to Drupal 7. If you test it and it works for you, please comment on that issue, the more people that review that patch the closer the module will get to a full D7 release.