Had not thought of this before, but this sounds like it would work better than RFID tags for proximity sensing:
http://www.sparkfun.com/products/8245Put Nike sensors in all your shoes, in the whatever software implementation, assign the various ID's to whomever pair of shoes it is.
for each sensor you get a receiver. Also get the USB adapter, and getting all the receivers to communicate with your HA server is up to you
I'm sure some of you VB experts could have this working in no time
http://www.sparkfun.com/tutorials/41