Webhook trigger when build is requested/scheduled

I am looking for a webhook trigger that fires when a build is requested or scheduled. I am writing an app that shows the build status and I would like to show when a build is pending state. Right now, I only get a notification when the VM is up and the worker actually starts the build.

Travis CI support team suggested implementing this with GitHub’s webhooks. For example, a push commit should generate a build so you could infer/assume that a build has now been requested. In my opinion, however, trying to infer this from Github webhooks is only a partial solution because it would not work if the user triggers a build manually in Travis. Additionally, it would make my app a lot more complicated because the user would now have to set up webhooks in GitHub as well.