this is sample code to attempt to launch native applications from mobile browsers with a fallback to the html page if the native application is not installed on the users device. NOTE: this code sample is not DRY - and can be optimized. This is an amalgamation of several SO postings on the subject matter.

gistfile1.js

var clickedAt = +new Date(),
    timeout, iframe, webURI, nativeURI;
// '+newDate()' is the equivalent of calling valueOf method
// of the Date Object. + is a unary operator. 
// see: http://xkr.us/articles/javascript/unary-add/

if (navigator.userAgent.match(/Android/)) {
    // Jelly Bean with Chrome browser
    if (navigator.userAgent.match(/Chrome/)) {
        // Jelly Bean with Chrome browser
        setTimeout(function () {
            if (+new Date() - clickedAt < 3000) {
                // window.open( url , '_blank' );
                window.location = webURI;
            }
        }, 2000);
        window.location = nativeURI;
    } else {
        // Older Android browser
        iframe = document.createElement("iframe");
        iframe.style.border = "none";
        iframe.style.width = "1px";
        iframe.style.height = "1px";
        timeout = setTimeout(function () {
            // window.open( webURI , '_blank' );
            window.location = webURI;
        }, 1000);

        iframe.onload = function () {
            clearTimeout(timeout);
        };
        iframe.src = nativeURI;
        document.body.appendChild(iframe);
    }
} else if (navigator.userAgent.match(/iPhone|iPad|iPod/)) {
    // IOS
    timeout = setTimeout(function () {
        if (+new Date() - clickedAt < 3000) {
            window.location = webURI;
        }
    }, 2000);
    clearTimeout(timeout);
    window.location = nativeURI;
} else {
    window.open(webURI, '_blank');
}