AdmiralAlkex

Add your username for Twitch and/or Hitbox (empty string to skip) to the settings.ini file and it'll alert you when the people you are following goes online.
Uses Livestreamer for playback if available (highly recommended) otherwise opens in your browser.
In comparison to similar scripts that I have seen posted here, this takes your username and pulls the people you are already following instead of having you manually entering everyone again, greatly simplifying things.
The Twitch and Hitbox API's were largely implemented by glancing at the python-twitch and Hitboxy python libs.
Forum thread.