We are currently working on exactly that. The idea is that we check your dependencies every time you push to GitHub. Here is the current status of that hook: https://github.com/github/github-services/pull/727. I hope to get it done next week.
Excellent! Looking forward to it :) I think the time-based checks are still relevant as well. The way I see it, Webhooks track added or changed dependencies during active development and the time-based checks make sure the project doesn't get stale.