Once you've setup your Heroku application, adding a webhook is easy.
Get an Auth Token
Generate an External Auth Token for your build server to use from your Raygun User Settings page
Jump into your terminal/command line and navigate to your Heroku application and enter
heroku addons:create deployhooks:http --url=https://app.raygun.com/deployments/APPID/heroku?authToken=EXTERNALAUTHTOKEN
APPID with the token from your Raygun Crash Reporting URL (
https://app.raygun.com/crashreporting/12345) and replace
_EXTERNALAUTHTOKEN_ with your external auth token.
Next time you push to Heroku, Raygun will be notifed about your change.