Couple feedback points.
1 - the ui in your screenshot on the home page (https://recalll.co/theme/flat/img/search.png), in the results section you have the title as blue. At least in safari, in real life its black. This makes the results all run together and visually be hard to quickly tell where one result ends and the next begins.
2 - if I was to use it for actual work, the search "nsfetchedresultscontroller duplicates" would be something that I have searched for recently. unfortunately nothing really useful came up on this recalll.co. Maybe a good example to test against google, stack overflow, and quora.
3 - not sure if the types of queries I want to put in to search asana or evernote, would be the same types of queries I would want to search the web / blogs / stack overflow. I suppose maybe the use case is, just use recall, and we'll figure it out. But sometimes I may want to search for something silly like "s3 credentials from bob", which might producer weird results in stack overflow for example, because there is probably lot of people talking about s3 credentials, but its completely out of context, and I would want the results from evernote or something. (whether evernote is a good place to store those of course is probably another discussion, but to illustrate the point)
4 - some people won't install chrome extensions. if I try to search right from your homepage, the animated help thing starts to overwrite my input. whatever I'm searching, if its not already open, I want to open it quickly, and execute the search immediately.
Great work though. The concept is cool. Maybe you could end up like duckduckgo, for programmers.