Okay, so you can use this to break up Joshua Jay's marriage—and that's a noble goal—but does it have any actual magic value?
Sure. Essentially it's a tool that can be used to get someone to confirm something that never actually happened.
For example, let's blow this up into a big Derren Brown-esque, mind-blower.
Your friend comes by. You force the 2 of hearts on her. As you gesture for her to grab and uncap a Sharpie, you top change it for the 5 of spades. You have her sign the back of the card and place it under her hand.
You say, "I'm going to record the details of what has happened so far so we can reference it later if we need to."
You turn on your phone, open up the voice memo section, and say, "Sophie came over. I spread a deck of cards on the table. She freely chose one card. It was the 2 of hearts. She signed the back and now it's under her hand. Is that all correct, Sophie?"
She leans into the phone and acknowledges that's all accurate.
You stop the recording. You ask her to keep her hand on the card, close her eyes and picture herself coming into your house, as she did just minutes ago. You ask her to be open to all sensory stimuli and really try and make the scene as vivid as possible.
When this is over you ask her to open her eyes and tell you what card she selected.
"The 2 of hearts," she says.
"Are you sure? You really feel it was the 2 of hearts?"
She says, "Yes."
"I'm going to tell you what really happened," you say. "You came over here, you selected a card. It was the five of spades, you signed it, and it's been under your hand since then. Take a look."
She does and finds the 5 of spades. However she's still adamant she picked the 2 of hearts.
"You didn't. Your brain tricked itself. You don't have to believe me. We have you confirming it earlier."
You give her the phone and she plays the voice memo where she confirms she picked and signed the five of spades.
You tell her you'll explain what happened and you point out all sorts of imagery around the house that have two hearts subtly or overtly displayed in them, you show her how the vacuum cord is laying on the floor in the rough shape of two hearts, you show her the last text you sent with the emoji with hearts for eyes, etc. etc. She absorbed all of this subconsciously, you say, and that imagery replaced the image of the card she actually took.
"Wait...," she says, "that's why you were playing that shitty Phil Collins song when I came over!"
The End.
You can figure out the details from everything I've written if you're so inclined. I haven't performed this myself. (I use the Jerx App for this type of effect. I think because it offers video proof, and it's on the spectator's phone, it's significantly more convincing.) But I do think it's structurally a pretty sound effect.
One thing to keep in mind is that you don't need to make the transition (the moment you actually hit record) happen right before they start speaking. It can happen at any point between sentences. So you could speak (set up the false reality), secretly hit record [transition point] continue to speak, maybe even set the phone down. (With the screen down or the screen off, because, when editing, the recording is red, not white. Most people won't know that, but it's just a consideration.)
