Hi, I don't think ArtRage will show up as a plugin as it's only a stand-alone app as far as I can tell.
I don't actually use Adobe Lightroom, but do use On1 Photo Raw, which is an app along the same lines as Lightroom. With that you get the option to send files including .psd files, to other editing apps by right clicking on the image. It's not quite as seamless as a plugin but it works fine. With Photo Raw if you have already edited the image you are prompted if you want to edit the original file.