From our friends at Random Good Stuff comes this lovely old article.It's a doorbell that requires the ringer to insert 10c in order for it to ring.
The idea is that only people who really want to see you will pay the dosh. I assume one would just give a welcome visitor their money back.
My solution is simpler ... I don't ever answer the door unless I'm expecting someone. My friends know not to drop in uninvited.
