You're correct. We need to put a clearer link on the site to it. Here's where you can download it from:
http://tsp.esta.org/tsp/documents/published_docs.php It will be under E1.20-2010
There are lots of architectural products making use of RDM, particularly color changing fixtures. It is attractive for architectural fixtures, where they need individually addressable fixtures without having to put a UI or DIP Switches that have to be accessed on the fixture itself.
There are messages in Sensors for monitoring contact closures or most any type of sensor you can imagine. You can then take whatever action you want based on those values. Suitability really depends on your application. In cases where you aren't constantly changing intensity values (i.e. a color changing fixture that has a constant color change effect running) and don't need a high refresh rate on the DMX data to maintain a smooth crossfade then you can allocate more time to polling for sensors/switch changes so you can then respond to them with a lower latency.