Here are the steps:
1) create a saved search in Splunk , with a sendemail command at the end.
2) Use method of your choice to kick off this saved search. One sample method is mentioned here.
http://dev.splunk.com/view/SP-CAAADQT
3) Have your external trigger, run the method of step 2.
First you need to create an alert which will look for desired URL and run a script. That script should handle to run your saved search and email the search result.