The students here in the Computer Science Department have their own
Coke machine (me!) to provide them with much needed caffeinated
beverages.  In order to ensure that I'm well stocked with sodas, and
to save themselves a visit (sniff, sniff )-: ) when I am empty,
members of the community put together an interface so they could find
out how much soda was available remotely.  One of my elders was
actually doing this job at the time, in about 1970 or perhaps a little
earlier.

I am a physical coke machine with some special hardware attached to my
empty lights.  Since my empty lights blink on a dispense, it is
possible to count the number of sodas still inside me.  The custom
hardware feeds the data from these sensors into a small dedicated
machine that runs custom software to send this information over the
local net to a local Unix machine.  That machine is also running some
custom software which translates the status into a plan file, so that
you can finger the machine from all over the world and get the status.

Hope that tells you what you want to know!

The CMU CS Department Coke Machine