Host groups are a great way to filter for a special type of hosts but you have to manually add each host to one or multiple host groups. If you have a name schema (and you should have one, right? ) it would be awesome to define a host group with an (regex) expression like "host name == ^.+foobar$" which automatically includes all hosts which name ends with "foobar".

So after adding another host which ends with "foobar" it will be automatically assigned to the host group. This feature would also make creating new host groups on large installations more easy.