They've been around in some aircraft and seats for at least a few years.... probably not a bad thing to have them on all seats if they work reasonably well.
Seem to recall sitting at an exit row with a large space ahead of the seat on an AC A321 a few years ago, that had one of these. Same company makes models for GA aircraft as well... 2 recent build Diamond DA40's at a flight school I flew at had these in the front seat as well.
Aviation Child Restraint - Aviation Seatbelts - Aviation Child Seat