Yes, the Rain Machine app continues to work, at least on Android. With the exception of Notifications. I reported this to them at the end of last year and they responded that because of changes to Android they needed to rewrite the Notification portion of the app. They also indicated they were working on it.
However, so far there has not been an update and my inquiry last week has gone unresponded to.
While I never used the plugin for Rain Machine, remote access still works (without a subscription), but you need to open a port in your router.