This can be done but what it will do is to track your all daily activities some of them which you might not want to consider. What @actifit does is to let you do activities on session basis just like if you want to record your running activity for the moment you start running, you just have to open the app and it starts tracking activities for that particular session. Hope it helps.
RE: Actifit Daily #44: Improved Graphics, iOS Updates, Daily Delegator Payments and more