I know there is this mod https://custom.simplemachines.org/mods/index.php?mod=1877 but it throws errors on installation (too outdated?). There is also this mod for Similar Topics https://custom.simplemachines.org/mods/index.php?mod=3473 but does not work for Sphinx.
Any ideas of how to implement something like that?
Sphinx appears to support autocomplete
http://sphinxsearch.com/blog/2013/05/21/simple-autocomplete-and-correction-suggestion/