@Josh1349 I agree that it would be a useful feature. For instance, I do a lot of communicating with my upholstery clients through whatsapp. It's great to be able to see the 2 blue check marks next to a message I sent them to know they read my message.
This isn't the first time this has been suggested on this forum.
One thing you can do is add to your guest messages, such as your check-out message, to please shoot you a quick return message or text so you know they received your message. Hosts sometimes get irritated that guests "ignored" a message because they didn't respond, but guests may not feel it requires a response unless you tell them.
For instance, a host may get miffed that a guest hasn't answered a "Hi, just hoping you checked in okay and are settled. Let me know if you have any questions or need assistance" message. Now if I received a messsage like that, I'd message back, " Yes, all is well, thank you." But someone else might not feel it required a response unless they actually had an issue.