A couple of weeks ago, on impulse, I picked up a package of CamiSecret (warning: perky promotional ad video at link) at Wal-Mart. I knew I could return them if I didn't like them, and for less than $10 I didn't figure I could go wrong.
Let me just say that a couple of days ago I was over at Rite Aid (local drug/convenience store chain) and when I saw they had the package of the other three 'basic' colors, I snapped them up!
A lot of blouse and dress styles nowadays are cut pretty low in the neckline, and if you have any sort of average-to-large sized bustline, you are flashing your cleavage to everyone......I don't mind a teeny bit of cleavage if I'm just at home working, but if I'm out in public (or at Church) I think I ought to be leaving more to the imagination, rather than running a full-color ad for the goods.
These little doodads are the perfect answer. They have permanently-attached snaps on either side of the top edge; these go around your bra strap. The fabric is shaped like a trapezoid with the wider (lace edged in the ones I bought; they also come with a plain edge) edge at the top, and the narrower one hangs down your top, blouse or dress just enough to keep it from flipping out of your clothes. They are made from fabric that's a bit slick but not obviously lingerie-looking; the CamiSecret stays put under your clothes and your clothing can move around and bit without being bunched up or dragging/pulling on it.
The fact that it fastens to your bra straps means that the top edge lays flat against your skin, so it conceals your cleavage and doesn't gap when you bend over or move. I have several camisoles that, if I pull them up high enough to lie against my skin, they might as well be a t-shirt. This is not the look I want!
I now have six of them - black, navy, brown, white, ivory and beige. I've worn them several times and really like them. They are not sweat-inducing and after a few minutes you forget they are even there. So now I can wear my v-neck and wrap-bodice tops and dresses without a whole other layer of clothing underneath!
Maybe you want people looking at your cleavage, but if you don't (and if you can't stand another layer under your clothes), try CamiSecret.
For folks who like, and can wear, other colors than the basic neutrals, they also offer a set of three different animal prints, and a set in three bright colors.