This add-on works great. A little tricky at first trying to understand what is needed to set it up, but once everything is set up - it works great. Maybe a small video to describe show how to set it up would help.
Remember you also need to have a calendar set up ahead of time in order for this work correctly.
The price for additional registrations ($5 for 5k registrations) is extremely reasonable as well. (You get 31 for free)
Additionally, I would recommend the developers add more options or additional examples for customizing the look of the available events that can be selected in the drop-down menu.