Googlebot requests page -> your webapp detects googlebot -> you call remote service and request that they crawl your website -> they request the page from you -> you return the regular page, with js that modifies it's look and feel -> the remote service returns the final html and css to your webapp -> your webapp returns the final html and css to Googlebot. That's gonna be just murder on your loadtimes.
If this must be done, for static pages, it should be done by grunt during build time, not by a remote service. For dynamic content, it's best to do the phantomjs rendering locally, and on an hourly (or so) schedule, since it doesn't really matter if googlebot has the latest version of your content.
Or perhaps I'm mistaken and the node-module actually calls the service hourly or so and caches results on app so it doesn't actually call the service during googlebot crawls. If that's the case, I take back my objections, but I'd recommend updating the website to say as much.