I have been looking for a customizable countdown timer in vain. So, I decided to develop my own! Thanks to some people who have provided the source code, I was able to come out with the first version, which, I hope would bring you some help. You can use it directly, or include it in your smart board software. Please, do not hesitate to provide any feedback.
This software is developed to help departments keep records of substitution and absence. You can download our school’s English Department (Arabic Version) here.