Chris Bell uses Powershell to alert us when the SQL Agent service goes down:
Now that we have our PS1 file that will send the email alert, but we need to have the job run when the service fails. To set this open up services and right click on the SQLServerAgent service you wish to add the failure alert to and select properties. Navigate to the Recovery tab and set one of the failure actions to “Run a Program” I tend to choose it as the first failure action as I like to look at why my service failed before I just restart it. You can attempt to restart first and then run the program on if it fails again by setting the second failure to run a program. The choice is yours!
Very cool.