This was nice and something we already had available because participate in Question point’s Ask US 24/7 service.
On a non-mobile browser you have a small chat window right away you can place in a corner of any web page. On a mobile device the script displays a large button to click to launch the mobile chat web app. The button actually takes up a larger space than it appears so we gave it its own launch page.
If you don’t like it’s launch page I did go farther and tracked down a more direct URL for launching the mobile app but it works a little differently now so the method that worked for me is no longer available.