What technology should I go with for developing a GUI desktop application across Mac & Windows that monitors all the other applications' activities?

I am doing my B.Tech college project. I want to make a nice GUI desktop application for Mac and Windows. This application should monitor my activities on my different machines throughout the day (want a system like a server here) e.g. how much time did I spent on an application-X, how much time did my machine stayed idle etc. I may want to extend the application to my mobile too. What technology/language should I be using? What is the standard practice?