I came across this app whilst training some students on the use of iPad in primary. We were discussing the use of other apps in sessions and looking at planning different topics. one of the students (Mel) mentioned a timeline she had seen so we searched and found this great app by ReadWriteThink.
As always it is an app I love because it lends itself to multiple applications in teaching and learning and not simply a one trick pony.
You can download it here
I will upload a screencast soon