I still think a long length of elestic firmly attached to the equipment library shelving is a useable and cheap solution that needs no extenal power.
For those with no sense of humour this message was sent with my toungue in my cheeek.
I have just been chatting with a syringe pump company person who says they are seriously looking at building RFID in to their pumps as so many people are asking about it. Well they would wouldn't they if they want a sale. But by us insisting on it, we get around the power/size/emf compatability issues if it is built in from the start.