Is a pendulum dangerous?

I went to a phychic fair yesterday and bought something called a pendulum. You hold it over your hand and ask yes or no questions, depending on the way it moves or spins it answers you. When I brought it home my fiance said something about it opening doors to the spirt world and that it could bring negative forces into the house. Now that I've researched it, it does say that it's sprits talking though it. My question is is it dangerous to keep it in the house, even if I decide I'm not going to use it?