Looking for a neat way to keep box lids closed, I started using tiny rare earth magnets. In small sizes, 1/8" to 1/4", they are strong enough to secure the lid, but not so strong that the lid is difficult to open.
Although I recess them so they're flush, and secure them with epoxy, it's still important to keep projects that use them away from children. There have been recent concerns about toys designed for adult use that contain multiple loose magnets. These have serious consequences for children who swallow them, especially if they swallow more than one.
To be on the safe side, it would be prudent to keep any project using these magnets away from children, and to advise anyone to whom you give or sell these projects to do the same. Since delicate or fragile items are typically kept away from children as a matter of course, it should not be a problem to add these to the list.