Add widget code to handle cases where iframes don't work.
wordpress.com blogs can't have iframes and I imagine that isn't the only place on the web. Would be nice to have the code provided that does basically <a href="link to graph"><img src="link to graph image"></a></img> (which is what I did for my blog post: http://blog.wraithan.net/2015/01/13/beeminding-zenircbot-3-0/ )
Even better would be if the url took parameters to tell it the size of graph to make (with obvious limits) so I can make a widget that fits nicely in a side bar of any width. Or make them a bit smaller to have two side by side in a post without making them tiny widget sized... etc.