Pecan, you said:
A while ago she felt guilty for masturbating repeatedly while having fantasies she thought were unbecoming for a married woman.
I just think that the first thing your wife needs to do is figure out whether chastity in itself turns her on, which is fairly common in both males and females. Or, on the other hand, whether she actually feels guilty about masturbation and having fantasies. It is healthy to explore a kink as long as one explores it safely, but it cannot be healthy to feel guilt about masturbation. I am no therapist, but I believe she should accept masturbation and fantasies as part of herself, just as masturbation and fantasies are part of everyone. There is no reason why it should matter whether a person gets aroused and has an orgasm alone or when their partner happens to be there. Nor does it matter what one imagines in order to get turned on and get off.
Perhaps your wife truly has no real guilt about masturbation, but has said that she does, as a way of setting the stage for the chastity fantasy. If that approach is part of what makes this game exciting for her, then there is nothing wrong with that. I just think that if she has real guilt about masturbation, she needs to find a way to stop feeling guilty rather than to stop masturbating.
Assuming that your wife has the right attitude about exploring chastity and that she does not really have serious issues about masturbation, I think that given your criteria, a very practical and convenient idea would be labia piercings. An extreme idea, perhaps, but so what? People get their ears pierced all the time. Another zity member mentions in a post on another thread that she started out wearing a chastity belt, but has since moved on to wearing labia piercings instead ( http://www.zity.biz/index.php?mx=forum;ox=display;msg=593061 ). You could probably ask her about her experience with this. Of course any piercing should be done by a highly experienced professional, in a professional setting. You can research more about that yourself, if this idea interests your wife. Labia piercings for chastity entail getting two rows of piercings through the labia, with each piercing of one row directly across from each piercing in the other row. After the piercings heal with a ring in each one, the woman uses one ring to connect each corresponding pair of piercings. Here are some links to pictures for example (of course, these are just examples and everyone looks different):
a history- with pictures of labia piercings, unconnected:
http://news.bme.com/2008/08/26/western-history-of-female-infibulation-outer-labia-piercing/
another example:
http://cs620424.vk.me/v620424831/d7e3/xZm2nu2tvms.jpg
labia piercings, connected for chastity:
http://fap.to/images/full/53/131/1310288627.jpg
http://fap.to/images/full/53/104/1040161512.jpg
http://41.media.tumblr.com/d272b6046a7aa25b4381ebb3979c7d0d/tumblr_mhqujrJj8i1qg4h3so1_1280.jpg