When you add customers to Waitlist Me, you have the option to send them a confirmation text with their estimated time or ETA and a link to check their place in line. Customers can press on the link to see the public waitlist in their phone browser. They don't need to install an app.
When you are ready for them you can send a text notification by pressing a button in Waitlist Me. They can also see the status message change on the Public Waitlist and send a reply through that page. All the text notifications are customizable with Waitlist Me Premium, and Waitlist Me Pro has more customization options for the public waitlist page.