A timer for keeping track of keyboard timing when mob programming, also works great for pair programming. Add your participants to the list, pick a time interval and get to coding!
Check it out at mobtimer.zoeetrope.com!
After the great Woody Zuill held a talk on mob programming at my place of work we started experimenting with it. We quickly noticed that having some type of timer was pretty much necessary to keep the flow going. I was into Ember.js at the time so I made a simple timer with participants and shuffle. It worked great and helped us greatly in our mob sessions. It also turned out to be great in pair programming.
A few months later React was the the next big thing. My colleagues where raving about how simple it was and how you could build complex frontend apps in no time. Basically what Ember.js was promising but didn't quite deliver in my opinion. I decided to reimplement mobtimer in React. To my surprise the learning curve wasn't as steep as Ember.js even though it's a very different way of approaching apps than the MVC that I was used to.
After a few short days I had all the functionality that I had in Ember.js and in much less code. More importantly the code was easy to understand and flexible. No huge rewrites required in order to implement new features and such. That is the version that I am hosting, both versions are on github (ember, react) if you want to see the difference.