Safety for Children riding as passengers

Hello all, my GF has the bright idea of taking the kids out riding with us. the boy can't quite reach around completely, and I recall seeing some contraption at the bike shop that had handles, and it was like a kidney belt and people could grab the handles to stick to you. Anyone know what that thing was called? I am looking for it on ebay or amazon, but i'm using bad description lookups or something, thanks!