SearchAmplius is a Cydia tweak that was released on the BigBoss repo recently that allows you to add custom search result sections to Spotlight utilizing SearchLoader (a developer library for implementing custom search results in Spotlight).
The SearchAmplius Cydia tweak adds 8 new categories to Spotlight searches that include: Cydia, Calculator, Weather, Stocks, YouTube, iTunes Store, App Store and Maps.
It is worth mentioning that some of the categories require an internet connection to be displayed and as such the developer urges you to sort them to be processed last. As for Cydia results specifically, they are refreshed every midnight or on install.
You can configure the order of results and filter out certain results in the SearchLoader preferences panel in the Settings app.
I have tested out SearchAmplius and can confirm it indeed works as advertised. Having extended search results in Spotlight definitely makes it more useful and may convince you to use it more often (I know it has for me).
If you are interested in SearchAmplius you can find it on the BigBoss repo for a price of $2.99. You will also get the SearchCollapse Cydia tweak for free (save $0.99). Be sure to let us know what you think of the tweak in the comments section below.