it is trivially easy for any node to broadcast its IP address to the whole network periodically (in my case every 2 seconds) using a separate thread and UDP. Using this technique I have rock solid ZeroMQ topology that reconnects with max downtime about 2.5 seconds (because I broadcast every 2 sdconds) for any single node failure. I agree that this functionality could be better implemented in zmq but using this simple technique, the rest of zmq becomes amazing. In Python:

  import socket
  import time
  cs = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
  cs.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
  cs.setsockopt(SOL_SOCKET, SO_BROADCAST, 1)
  while True:
      cs.sendto('Node ID', ('255.255.255.255', 54545))
      time.sleep(4)

Everybody listening on the same on port 54545 without knowing Node ID's IP address will get these messages which includes the broadcaster IP address.

  import socket
  s=socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
  s.bind(('',54545))
  m=s.recvfrom(1024)
  print m[0]

This is a very useful technique when using ZeroMQ generally as you can broadcast services without knowning any IP address so they can come up and down on new addresses if / when necessary.