$(document).ready(function() {
    $.ajax({
        url: "http://www.strava.com/stream/segments/860503&callback=?",
        dataType: "json",
        success: function(data) {
            $(document.body).append(data.latlng);
        }
    });
});

$(document).ready(function() {
    $.getJSON("http://www.strava.com/stream/segments/860503&callback=?", function(data) {
        $(document.body).append(data.latlng);
    });
)};

myCallback({ ...... });

$(document).ready(function() {
    $.getJSON("http://www.strava.com/stream/segments/860503?callback=cb", function(data) {
        $(document.body).append(data.latlng);
    });
)};