Yeah, there are many ways to get his attention. Find a smoking hot picture of your wife for a wallpaper. Maybe even something with her wearing on teddy or sexy bra panty. If bold enough and you know your going to their place, put a hot nude of her on your wallpaper. Which of course you will be checking your messages every other minute which gives him lots of chances to see your wallpaper when you pull your phone out.
You could just get to the point and ask him if he has ever caught his wife with someone else.. then let it lead to confessing that you had had these weird thoughts that you walk in and your wife is on the kitchen table being a slut for (the neighbor, plumber, milkman, whoever) a Casanova. Gage the conversation and let it be one of those BRO talks about how you know she is FUCKING AMAZING and that why wouldnt any man try to seduce her. Indicate that you know she is hot and you get horny thinking that she is some Big Porn Star like Tracy Lords or Hot like Angelina Jolie. You see other men looking at her and it really kicks your confidence into High gear. Be all innocent but leave the door open for him to ask you more in the future. You can even bring this up while his wife is part of the conversation but I would not as women talk about what they find out about us.
