The Interactive Touch Books app that is needed is free and device requirements are: Compatible with iPhone, iPod touch, and iPad. Requires iOS 4.0 or later.
Lastly, a child who needs to learn the numbers 1-20 and basic colors is super young - probably around 3. A child who would be able to learn the signs in the videos correctly without further direct instruction would be much older. Rating: 2.5/5 (based on topic, aim for around 4 years)
Balance: As mentioned, rather than or in addition to the hotspots on each page when counting the objects, I'd add a verbal and visual counting cue. Also, the later pages start to double up the numbers (# 13 and #14 are on the same page), so it starts looking a little cluttered and the number of objects increase. Rating: 3/5
Sustainability: I usually don't comment on the production quality, but I did notice a gap between the nice pictures and hotspots and the lower quality in voice over and ASL videos. I think this will make kids concentrate more on the hotspots (which they love already) rather than wanting to see the video. There's nothing really that ties the rest of the book in with the videos, so what would lead kids to play the videos that don't look as cool as the rest of the page? So although kids might want to continue tapping on the hotspots, I don't know if they will watch the videos enough to learn the signs - which I feel is the goal of the app. Rating: 2/5
Parental Involvement: The ASL videos could be a conversation starter and would definitely need some attention and reinforcement from parents. Rating: 3.5/5
Total: 11 out of 20 = 2 stars
Disclosure - I received this app for free for review purposes.