Martin Schöneck has created a neat set of scripts and supporting files that allow the creation of EMC2 HAL files from Eagle schematics.

Martin seems to have found a way to express all of HAL's important features (parameters, pins, modules, threads, functions) in Eagle schematics.

http://martinschoeneck.de/hal-write

Personally I like the idea of using an existing schematic layout program for this task, instead of creating all-new schematic capture software.
-- Jeff
(originally posted on the AXIS blog)