While not fully supported, owing to the fact that you can make requests which would cause lots of memory usage or resource consumption if you’re not careful, it sounds like what you want is TAP. See:
Note that the Java client (couchbase.com/develop/java/current) has TAP implemented. Use it with caution and at your own risk. As long as you stay away from checkpoint and registration, it will generally be okay but can cause quite a bit of disk IO if you have much more data on disk than in memory.
Updated Sept. 2016: TAP has been updated some time ago (around Couchbase server 3.0) with a new protocol called DCP. The Go client now has DCP implemented as an unsupported/uncommitted feature. There is also a new Java DCP client as a separate library, also unsupported/uncommitted.