The woodworkers here, at least those with all their fingers and/or intending to keep as many of them, we know what it is. For those who don't, this replaces the need to have fingers close to high powered blades.
This thing is amazing. No more fidgeting with tracks and buying multiple adaptors. This is reversible and can be placed on any magnetic surface with sufficient hold to be effective.
I've used this Featherboard without noticeable movement when ripping huge 20mm+ MDF.
It is not an electro magnet either so no need for batteries.
Normally $159 at Carbatec, $149 at Timbercon. Both ex shipping.
Aussie product sold through Amazon US (sadly, it costs more here).
Other Magswitch options available too.