MyTameables

A plugin with the only purpose being teleporting your tamed animals to your position upon chunk-unloading.

The plugin is a simple plug-and-play, so no need to play with the config.

The technical:
The plugin checks for all Tameable entities which ALSO are an instance of the Sittable interface upon a chunk unloading.
Once the chunk-unload event is triggered, the plugin checks if the owner of the entity is only, at which it checks if the entity is sitting OR if there is a jump between worlds (in which case they sit on World change, so we skip the sitting check).

The plugin then looks for a safe location for your little pet, starting with your current player location, and if that is not safe, checking all coordinates from Y 255 through Y 1. There is an option to use a more expanded search, which also searches in a two block radius (in the two-dimensional plane), but that is disabled by default, as it takes quite a lot more resources.

Known issues:
If an entity (mostly multiple entities) cannot teleport to your location, and multiple chunk-unload events have been triggered, you can experience the Error message for an unsuccessful teleport multiple times.

For compatability with MyDog:
If you use this plugin alongside MyDog, please deny the teleportation permission for the Players. If there are enough people wanting it, I can implement a check into MyDog which looks for MyTameables...