Teaching early numeracy is can be challenging; one to one correspondence, base 10, addition.
An app was just released that allows students to count on their fingers. Finger Count - Mulit-Touch by Joe Scrivens asks students to count objects shown and then place that many fingers on the screen. It allows for any combination that equal the number shown.
This app makes unique use of the iDevice's ability to process multi-touch input. The iPad can handle 10 touch input points while the iPhone and iPod Touch can handle 5.
It has the option for students to count each object individually by tapping on them in any order while it counts out loud.
This offers teachers a new and unique way to transfer mathmatics learning from object manipulatives to the iDevice.
There is a great introduction video on youtube that explains how it all works.