Visual tracking of workflow is really a useful thing to build into your systems. The list of gotcha’s in the slides and others I’ve found since, mean that this particular approach using the rehosted workflow designer, while viable in certain cases, is probably going to take more work to make it generally usable solution for visual tracking of workflow. The idea presented here to use a custom tracking participant and SignalR to broadcast workflow tracking events is simple and solid and with a little more goo to pick a “topic” using groups or hubs would work very well I think. A little care will need to be explored to account for scaling if you’d do this with hundreds of users based on the overall design of signalr.
I also would like to point out a few other related projects, one that used a service bus instead of signalr and another that used signalr, but not a wcf behavior or visual tracking. Enjoy your reading!