How do I find a surveillance bug in Grandad’s house?

I know for a fact my evil cousin has bugged his house, when I looked up surveillance equipment I learned that they can monitor conversations through clock radios, power strips, quarters, calculators......How do I know if my calculator is listening to me? How do I know if this is surveillance equipment? Do I have to call a specialist, if so, what specialist?
What if it's a digital gsm bug that transmits to a cell phone, would it still affect the AM radio?