I ran across this reference on Bikes in the Fast Lane.
I have never used this the BackRider and am not endorsing it, just providing information. I'm not a fan of strapping the kid to me, but I can see that some parents might want to try this. I think it would be useful on a snowmobile.
For the first couple of years riding with Lisa, I wore a belt that contained two sets of handles for her to hang on too, one set right in front of her, and another set out to the side. I see that the BackRider offers a set of 'cosmetic' handles this is unfortunate, a child should get used to hanging on in a functional manner. A child needs to get accustomed to the the acceleration and deceleration, a passenger should actively prepare for both, not sit passively waiting to crash into the driver. Perhaps different riding positions warrant less activity.
And as usual I strongly urge you and your passenger to always wear a full face helmet. Look for junior helmets when the kids are still small. And make sure they can reach the pegs on the bike for stability.