My daughter received an interesting gift for Christmas: a personal journal with voice authentication security. This little toy, called Password Journal, allows the child to record a spoken word of his or her choosing, and then access the journal with the same spoken word. If someone besides the registered owner tries to access the journal a chirpy British female voice exclaims "Intruder!" and a siren-like alarm goes off. The journal also recognizes a small number of voice commands, like setting the time of day and turning on/off an alarm.
In fact, the toy is a little hard to use for a child, and even for many adults. To get geeky-technical about it, the failure to enroll, false alarm, and false accept rates are pretty high. There aren't a lot of writing pages inside the journal, the novelty is in the voice activation itself. If you read the reviews by following the link, above, there's a lot of dissatisfaction with the product.
I helped design a voice authentication security system that is in use by a financial institution. I've also conducted research into consumers' acceptance of voice authentication. At the time the research was done (2005), people were still suspicious of VA, uncertain about its usability and effectiveness as a security solution. If people start growing up with toys that include VA, there won't be any novelty to it when they encounter VA in financial and other self service IVRs. Of course, if the toys don't perform properly then people may reject VA based on their previous experience with it. It's an interesting idea, though, that acceptance of VA as a security solution could be affected by peoples' experiences with childrens' toys.