I just released version 1.0 of GithubNotifier, a little menu-bar app I've been tinkering with for the past week or so. It uses your Github username and API token to check your repositories for any activity in your networks.
There are some caveats though. For starters, the network data API from Github doesn't show what branch a given commit was made to, so if I pushed an update to branch
development, the API simply details the commit, but doesn't include which branch. When the Growl notifications are made, a click-back is created so that if a user clicks on the message your default browser will open to
user/repo/commits, but if the commit was on a separate branch, you wont see it initially. You may have to look around in the branches to see more details on it.
I have a support request in to Github to include branch and owner information in the commit data returned in the network API call, but they may or may not choose to implement it.
You can checkout or fork the project here, patches are welcome.