EDIT: There was a bug that is fixed in 1.32.0 (that is pending review in Mozilla Add-on Store review queue).
EDIT 2: 1.32.0 is now finally available.

Live Content monitoring does work e.g. on http://bitcointicker.co/ (monitor bitcoin price). If it doesn't work for you, there might be an issue with the tracker setup or the website. Either way, please send support requests to nodetics AT gmail.com instead of putting them in reviews.