How about, if the wife who is not fasting gives oral sex to the husband who is fasting without ejaculation taking place? Is it permitted?
Scholars say that as long as neither of the husband or wife had ejaculation due to sexual arousal their fast is valid (assuming even the wife was fasting). (See this or this fatwa in Arabic or this in English) Note that the fast of any of them would only become invalid once a ejaculation takes place. And in your case only the fast of the husband could become invalid, as the wife isn't fasting.
On the other hand oral sex is considered by some scholars as an act of bad taste and is allowed under the condition that wife accepts this and is sure not so swallow any impurity. (See this fatwa in Arabic)
Note that fiqh scholars defined fast as the abstention of the desires of the haunch and stomach one should really not play with fire in Ramadan and keep away from it until one is allowed to do what ever one wants (during the nights) (as sassir quoted in his comment).
See also this fatwa on intimacy while fasting in Ramadan. Here a quote:
The view that masturbation or intimacy with one's wife to the point of ejaculation are among the things that invalidate the fast is the view of the majority of scholars, including the four imams, Abu Haneefah, Maalik, al-Shaafa’i and Ahmad. They quoted as evidence the fact that it is satisfaction of desire, and that is forbidden to the person who is fasting, because Allaah says, according to the hadeeth qudsi about the fasting person: “He gives up his food, his drink and his desire for My sake.” Narrated by al-Bukhari
And Allah knows best!