A few weeks ago we highlighted a project that helped you see diff's (aka pending changes, etc.) as you code for your Git projects, Get live diff's with Git Diff Margin Visual Studio Extension.
Well what about TFS projects?
A Visual Studio extension to display TFS Pending Changes on the margin of the current file.
Quickly view all current file changes on the left margin and on the scroll bar margin: blue rectangle for modification, green rectangle for new lines and red rectangle for deletion (color settings).
Please report all problems or feature requests you might have on the following page.
I did have to chuckle that this project is hosted on GitHub... Anyway, the Solution downloaded and built with no problems
If you're still thinking about creating your own margin VS extension or are interested in see the client side TFS API in action, this is a project you'll want to check out.