If someone calls you on your cell while you're pumping gas, there's a risk the spark between two electrodes generated when the phone rings can ignite the gas vapor around the pump handle, causing an explosion. Especially if you keep your phone in your pants pocket. And yes, it has happened. It's a completely different issue from electronic interference with other equipment.
This has been shown to not be true. The issue keeping in pant pocket is not the phone itself. Its static electricity.