I've actually had the idea to make beaded bookmarks for awhile, but several things held me back.
First was the fact that I think they're a bit thick to use in books. I mean, it's not like you're trying to stuff a Lego between the pages of your book or anything, but it is a wee bit broader than a bent corner or a thin plastic bookmark like I used to
The second thing holding me back was the price. I know I used to buy perfectly functional bookmarks five-for-a-dollar, so while I realize that the price on bookmarks in general has risen, I personally feel no need to pay much more than that for them. Certainly if it came down to paying $10 to hold my place or ripping the corner off a piece of junk mail to do the same job I know what I'd choose. So I took this question to Etsy as well.
Apparently people will pay lots of money for bookmarks--or at the very least people will list bookmarks for $20 or more, and for the purposes of my research that's almost the same thing. This adorable little thing isn't worth $20, but it does have $10 worth of work and quality to it.
Even if it won't interface with a Kindle.