How Can I Trigger The Client Side App From The Database

So my app has two separate pages which access my database. One page is a booking form and the other is a booking application.

When a booking is made and added to the database, I want the booking application to be automatically updated… so effectively for a trigger to come from the database to tell the booking application a new booking has been received.

Is there a clever way to do this?

The only way I can think of is to have a timer in the application which keeps asking the database if there is anything new to upload…

Best wishes,
Antony.