The Shimano Alfine chain tensioner, intended for use with Alfine internally geared hubs, is a dual jockey wheel spring-loaded mechanism that allows the use of multiple chainrings.
Any IGH can be used with multiple chainrings if it is equipped with a cog that can be used with a 3/32" chain and a rear derailleur or similar chain tensioner. However, most IGHs have a published minimum primary drive ratio and this should be respected in all available gear combinations.