Sadiq Khan, the current Mayor of London, was [spotted](https://politics.stackexchange.com/a/54874/29011) riding a (strikingly regular) bike around in May 2020.

What is the contraption attached to the center of his handlebars?

[![odd contraption attached to center of handlebars][2]][2]


  [2]: https://i.sstatic.net/IP2EN.jpg