LANBroadcaster, originally created by Ruan allows a Minecraft server to be broadcasted over the local area network and appear in the LAN server list without actually adding it.
The original LANBroadcaster, by Ruan has support for Spigot and BungeeCord, however this version adds support for Sponge and Velocity.
LANBroadcaster can be downloaded from the releases tab here.
Once it is downloaded, simply place it in the relevant plugins folder and start your server. No configuration is required.
Note: To use LANBroadcaster with BungeeCord or Velocity, you do not need to install it on the servers itself. Only the proxy.