Paranormal Pendulum

So I am planning to introduce a small little ritual involving a pendulum and giving a bit of your blood to check if the area you're in inherits or inherited some paranormal activity. May be also how strong the activity is/was ,basically a supernatural geiger. this ritual should be easy and mostly riskfree and will not involve any chanting? any vetos?

I like that idea. The ritual is very vague and simply gives you an indication of something that you probably knew already. It just serves to confirm a character's fears.