We’ve had the new extensibility on VSTS for some time now, including the ability to create dashboard widgets. With TFS 2015 update 2 the same extensibility became available to our on-premise TFS and with TFS 2015 update 3 we now also have support for custom dashboard widgets.
Give this we just released an update to the Countdown Widget which adds support for on-premise TFS installation, which has been a much asked for capability.
Get the latest version from the Visual Studio Marketplace: https://marketplace.visualstudio.com/items?itemName=ms-devlabs.CountdownWidget
If you are curios how the widget is implemented then I recommend taking a look at the articles Wouter de Kort and I wrote a while back: