Exotel provides popup notifications for both incoming & outgoing calls. As soon as I come to office, I login to exotel and then I get notifications like this everytime I get a call:

An interesting use of this popup is that if your addressbook has the name of the customer calling, then it automatically shows up in the popup. Using this, you could now say something like: "Thank you kumar for calling my company, How can I help you?". This personalized service delights your customer!

Now, lets say you have your own CRM, then you could attempt to implement your own popup service inside your CRM using the "Create popup..." option in your connect applet. It looks like this:


You put in a URL that will receive a HTTP Get request just before sending an call to an agent number. The parameters that you would get are explained here.

This is how the flow of control would be:

Customer calls --> Exotel receives call --> Exotel GETs your URL & simultaneously sends the call to your agent  --> You push popup to your client on agent's laptop. 

Example Tech stack that would be required to popup information in real time:

1) Node.js service that maintains a socket to user map like shown in the diagram below and does something on receiving an event to be sent to the browser in real time.

2) Socket.io on the server (for interacting with the browser) + browser (in-order to receive real time notifications)

3) Some browser side js/css code to pop-up or alert the notifications (the chat style pop up)