I was discussing this as a startup opportunity with a friend a couple of weeks ago. No surprise that others have decided to execute on it. It's not clear if they are any further than having just launched a landing page as their MVP, however.
As one of the comments on Hacker News puts it:
I bet we're going to see a bunch of "Heroku for X" now that they've set a precedent. I'm not sure that's a bad thing; it's a great idea.
Another entrant in this field is NodeJitsu, who started a few months ago this year, and, of course, Heroku themselves, who announced experimental node.js support all the way back in April this year.
It's going to be a crowded field soon, but one thing it certainly points to is that node.js is on the way up.