Very handy little wrench or handle for standard 1/4" hex bits. Great for accessing hard to reach areas where a standard length or stubby screwdriver may not fit. Not intended to exert a lot of force but for installing or removing fasteners which are hard to access or impossible to see (such as behind a dash).
Designed for a 6mm x 1.5mm Rare Earth Neodymium Magnet easily found on eBay.
Back side has a recess for spinning on the end of one finger.
Following video has details:
Finger Hex Wrench