I recently released Khoj for Obsidian. It enables semantic-search and find-similar-notes for Obsidian. Your notes stay private as all search and indexing is done locally on your machine. And the search is incremental, so you get a search as you type experience.
Hopefully that provides some of the Mem X type functionality folks were interested in using from within Obsidian?
See my announcement post for more details about Khoj