Blackboard / Math! is a mobile application targeted at elementary school kids to help them learn their math tables.
The application can run on many modern mobile devices (most devices that uses webkit). The primary development plaftorm is HP webOS. In its current state, the UI looks good on small displays. Work needs to be done for larger screen devices such as tablets.
It is build using the excellent Jo Javascript application framework.
If you use Google Chrome or Safari, you can try it right now!
Try Blackboard / Math!
Note that it works best with a touch enabled platform (there is no keyboard support for entering numbers).