Send emails to registrants who do not check in or turn up for booked event

We have an issue with people who book on our events but then do not turn up. This can deprive other people being able to attend the event.
This problem relates to members who can get in for free. 
We would like to be able to automatically send an email to registered participants who do not turn up or check in for our events.
This would act as a deterrent to people if they do not turn up from booking future events as they will know they are being monitored.