Talking about the relationship between I Ching and Taoist yoga, one cannot miss this famous book 周易參同契 (or shortened as 參同契 - Can Dong Qi)。 An English translation titled as "The Secret of Everlasting Life: The First Translation of the Ancient Chiense Text of Immortality" will be published in 2011. This unfortunately is a highly complex book, that, again unfortunately, has labored many scholars and practitioners for centuries, trying to dig out something useful there. I mean, like fallen into an (Eastern) abyss, can or can't get out is of course none of the business of the author, alchemist Wei Boyang in the Han Dynasty.
Talking about complexity, recently I came across a Taoist yoga book called 天仙金丹心法 ("Insider techniques for practicing Golden Flower [Dan] immortality", no English translation yet) written by a group of Tao yogist of same lineage in the most recent Qing Dynasty. As if in response to the complexity of Can Dong Qi, a large portion of this manual was written in different anagrams. A practical joke may be, or a way to safe-guard some insider techniques. This manual has been deciphered by a modern Taoist named Song Fei， and he published his work under the same name.
Taking about the influence of I Ching, we can still see it today, like the new English translation that I mentioned. Indeed there have been many studies interpreting Can Dong Qi, like one by the famous Chinese classic author Nan Huaichin. And some western Tao yogist call their practice Kan and Li - of course, how much, if any at all, they understand I Ching is beside the question.
Zen master and Taoist yoga master Liu Huayang, author of Hui Ming Jing belonged to another stream of practitioners. They prefer demystify rather than mystify. Liu Huayang (柳華陽) and his Master Wu Shouyang (伍守陽) wrote a few texts on the subject, and is now generally known as the Wu-Liu sect (伍柳派). Accordingly to them, their grandmaster Qiu （丘処機 - grandmaster of 龙门派） started this trend of demystification. Master Qiu was a figure made legendary through the highly popular fiction 射雕英雄传 "Legend of the Eagle Shooting Hero"). It is interesting to note that Grandmaster Qiu taught in foreign (non-Han-Chinese) lands, first in Jin Dynasty (that drove Han-Chinese to the South) and then in Yuen Dynasty (the Mongol empire that ruled China as a complete Dynasty, Master Qiu was highly popular with the Yuen Emperor). In other words, master Qiu demystified ancient Taoist practice and texts and spread the teachings to foreigners.
I find it interesting to compare Grandmaster Qiu with Richard Wilhelm who translated Hui Ming Jing (written by Liu Huayang a lineage practitioner of Qui) and spread this profound teaching to modern western readers. Even more interesting, Zen practitioner Charles Luk (encouraged by Carl Jung) later translated the book Taoist Yoga （性命法訣明指）. The author of Taoist yoga master Zhao bichen 趙避塵 was a lineage practitioner from Liu Huanyang - actually Chao learned from a lineage student of Liu - Zen master Liao-ran (了然)!
In conclusion, it is up to each modern man who is interested in this ancient practice whether to follow the complex way (like studying "Can Dong Qi" 參同契 ) or the simpler way (like studying "Hui Ming Jing" 慧命經).