ZadZack wrote a review of Eagle Creek Silk Undercover Bra Stash on June 30, 2014
Familiarity: I've used it once or twice and have initial impressions
Neat compact solution for a credit card or a bit of cash, but not for smaller frames. Tends to be noticeable under shirts for at least A-C cups.
Personally, I have little use for this stateside. I would prefer a different solution that could hold a passport.