Available in R3 2018 as part of the features set of the new and improved RadAutoCompleteView control, for more details on it refer to: https://docs.telerik.com/devtools/xamarin/controls/autocompleteview/autocompleteview-overview

As to the concrete feature go to: https://docs.telerik.com/devtools/xamarin/controls/autocompleteview/autocompleteview-methods