How can I send a message to a Join device from EventGhost?

You can’t use the AutoRemote plugin to send messages to Join, but you can use a simply python script 😁
Add a Python Command action in EventGhost and then use this code:

import urllib2;urllib2.urlopen("https://joinjoaomgcd.appspot.com/_ah/api/messaging/v1/sendPush?text=Hello&title=Title%20cool&deviceId=YOUR_DEVICE_ID&apikey=YOUR_API_KEY").read()

You can generate your own Join URLs here: https://joinjoaomgcd.appspot.com/