Answer:
A mechanism to discover who is following you.
You can do this with your friends. You can do this with your nose. But don't do it with your friend's nose!
The profession of Jimi Hendrix and Eric Clapton
A beautiful succession of sounds.
What must be looked through in order to see?
When is it bad luck to see a black cat?
Easy
Animal
Difficult
Food
Funny
Kids
Logic
What am I?