Recognizing the Third in Monogamous Relationships

My latest DatingAdvice.com post is live: Can You Be Monogamous and Attracted to Other People? (I like my title better, haha) I based this post off of Esther Perel's Mating in Captivity, in which she mentions the specter of "the third" (i.e. other people you may be attracted to) and how some couples choose to ignore the third, recognize the third, or invite the third in to their relationship. I wanted to explore some ways that monogamous couples could push the boundaries of their relationship to incorporate sexual explorations, and deepen their sense of honesty and trust.

Here's my intro:

In Esther Perel’s “Mating in Captivity,” she discusses the “shadow of the third.”
That is the fact that even when in coupled relationships marked by commitment and love, we often (maybe always) find ourselves attracted to other people.
By acknowledging the third, keeping your communication transparent and striving to know and understand your partner and yourself, cheating may be less likely to happen (thus preserving the commitment to monogamy you both have made).
What are ways two people can be sexually monogamous, but widen the door for more honesty and trust around sexual desires, fantasies and exploration?
The foundation for this is solid trust in your partner and relationship as sexually monogamous and a healthy way of managing your jealousy and insecurities.
I also believe it is a privilege to learn new things about someone, not a right. Being in a romantic relationship doesn’t give you the right to know about your partner’s private sexual thoughts.
If they, and you, are able to share this information, you should take it as a sign of the health and resiliency of your relationship.

I go on to offer the following ways that couples can be monogamous but add honesty and new sexual flavors to their lives; make sure to go read the post on DA so you can see my further explanation!:

Having opposite sex/opposite gender friends
Reminisce about the past
Watch porn and read erotica together
Share fantasies and attractions
Is flirting ok?
Visit strip clubs together
Visit a swingers' club or party to watch and be watched 

I would love to hear from others: what are other ways that you can be monogamous and recognize "the third" in your relationship?