ECB, or the Emacs Code Browser depends on CEDET for the semantic parsing engine, and several other features. ECB can display a window that shows semantic tag information.
ECB can also be used with JDEE.
In addition to the basic CEDET configuration, you will likely want to add the following Semantic configuration to your .emacs file.
(require 'semantic/canned-configs) (semantic-load-enable-code-helpers)
or the fancier
(require 'semantic/canned-configs) (semantic-load-enable-guady-code-helpers)
See the see Semantic Configuration. section of the semantic manual for more details about these features.