Ethereum Gas Watcher от Matnad

A browser addon to display the latest Ethereum gas prices provided by gasnow.org.
Additionally, it is possible to set alerts that send notifications if the gas price drops below a certain threshold. Rightclick a gas price speed level to set up a new notification.

The badge will show the current gas price (updated once a minute and when clicked) and the selected speed level (rapid, fast, standard or slow).