Henry nodded, and without thinking began to give her his cell phone number. He stopped himself, thought about it for a minute, and then pulled out his cell phone. "Do you know of any spells that allow instantaneous communication with someone else? These are like that, only they use technology instead of magic. They're called cell phones. Each phone is assigned a number, and when you dial a number on yours and hit send," he flipped his open and showed her the send button, "it will connect you to the person who has the phone that was assigned that number."
Then he pulled out his pen and pocket-sized notepad and wrote down his number. He tore the sheet off and handed it to her, depositing his phone, notepad, and pen back into his pocket. "Call this number if you need to talk to me, and unless I'm, uh, indisposed, I'll answer." He figured indisposed was better than saying "unless I'm being murdered by a cultist". Statistically his profession did tend to lead to that sort of problem.