I have a fantasy I enjoy with a friend, but it could apply to any wife or GF, of course...
We want to go to a club that has music and dancing; not a rowdy place, rather one enjoyed by a more middle-aged crowd. We enjoy a drink or 2, not only to relax her, but lower her inhibitions as well.
She can then cruise about the place, looking for men to dance with. Naturally, it is quite the turn-on for me, as I watch her share her intimate 'space' with him, and the touching. She is quite busty also, and loves to show her cleavage off, so I can see them staring at her tits while she pretends not to notice. I will also see how they try to cop a feel, seeing where they can place their hands on her hips without her objecting and trying to cup her ass.
If there is some genuine mutual attraction, she can bring him back to our table for a drink, sitting next to him instead of me. If she is flirting and/or trying to seduce him, I have to watch for the signs of him touching her under the table. The intensity goes way up if it happens to be a night where she wears a skirt with nothing underneath it!
When she tells me they are going to go outside to smoke, that's our code for "I'm going to give him a blowjob in his car", and I have to sit, alone and uncomfortable, waiting for her return. They may even return to our table after she has finished, especially if he is a candidate to go to our hotel room and perform cuckold/3-way sex.
If this worked to perfection, she would be able to enjoy a variety of partners, find the ones she likes, and "go outside to smoke" 3-4 times over the course of that evening.