Sure, re fview-lab, as you describe, it lets you run client-side Meteor code with per-key-stroke client-side recompilation. The idea was indeed that the snippets could be embedded in other sites and each lesson appeared with a screenshot of what the final code drew on the screen (being made for famous and all).
Unfortunately it went offline when Meteor ended their free hosting, but you can see it in action at my London talk at https://youtu.be/zR63GD9aeKw?t=975. Source code at https://github.com/gadicc/fview-lab.