Forgive my exhumation of an old thread. Sometimes a year or two makes new answers!
I found this thread in a search because it is very nearly exactly what I want to do. It looks like the guy joined made a post and left. For what I want to do, I bet there have been some technological improvements and price drops to make it more viable.
All I care to do is have a USB interface to Xbee wireless to Xbee to serial display with minimal power needed on the door unit. Then again, we can get some decent storage of power on the back side of the door with a few D cells.
In our building folks put post-its with their status. One group in the building has a bit more sophisticated looking 1" x 4" slot for those engraved plastic signs saying, "In phone conference", "out", "in", "do not disturb", "come on in", and even one had "disturbed", particularly appropriate for that guy's status, heh.
Changing those wirelessly from their desk via a Window app talking through USB to Xbee, and the novelty of using any kind of lighted display would make them very popular.
To take it a step further, we have a centralized office sign-out boards that have columns for in/out/lunch/home, a section for destination or other notes, a column for return date/time, and another column wherein most put their mobile numbers. Dedicated aren't they?
Anyhow, the height on those boards is 1" per row so a 1"x20 or 24" strip display could handle all the columns. Signing out from the desk would even be better for these.
Given all of this, anybody got some cheap hacks or ideas? I have seen where some outfit wants wireless name tags for conventioneers. Nice novelties for the market I'd expect.