Activity Indicator is an HDD activity light for your Windows device that is missing a physical one.

One of the things you don't get with a minimal computer like the Compute Stick is a Hard Disk activity indicator light to know when the machine is busy reading some stuff and wait for it to finish. Well there's an app for that of course appropriately named Activity Indicator found over on Sourceforge. You can see it in action (or lack thereof) on the image below and you can access it's full potential by right clicking on the icon and selecting Show Window to get to the main menu. It also has logging features that I don't use cause frankly I don't need them and they seem to crash the app sometimes.

The little green dot that is currently off shows the activity

and this is the on state..

There are other functions like logging available through the menu