It's free and has an in-app purchase to unlock additional functionality, but you can get a good idea of the app without the need to upgrade, so if anyone checks it out and has any feedback for me, I'd love to hear it.
My kids (aged 6.5 and 4.5) love using the app, especially asking how long it is until Christmas and how long it is until their bedtime (they know if they're late to bed they'll get the frowning clock), so hopefully your kids will enjoy it too.
Also, for the month of December, 5% of profits will be going to 'Sids and Kids' who are dedicated to saving the lives of babies and children during pregnancy, birth, infancy and childhood. Visit www.sidsandkids.org for more details about them.
Like I said, all feedback is welcome so please don't hesitate to comment below with any feedback you have. Thanks in advance.
p.s. Also check out the promo video featuring a Nexus 5: Kids Voice Search (Android app for kids)