OilCan inserts some powerful buttons into normal websites, and that power comes from Android intents. We didn’t write a barcode scanner or the radar app into OilCan, but using intents we can launch those apps with parameters. We can request the Barcode Scanner app to scan something and return the code to us, or launch the Radar app with a specific lat/lon.
Userscripts can do other cool stuff, like hide the navigation columns in Wikipedia to make it easier to view on small screens. This is a proof-of-concept for now, and will probably turn into a binary plugin for the default Browser in the future.