I'm working on a cross platform app for Android 2.2 and iOS 4.1 (dev devices). On Android everything works fine (accelerometer and geolocation) even if it's a little laggy.

On iOS it's way more smooth, but he doesn't call the Phonegap functions. That's my JS code:

var watchID = null;
var shaking = {
    left: false,
    right: true
};

function startWatch() {
    // Update acceleration every 100 ms
    var options = {
        frequency : 100
    };
    watchID = navigator.accelerometer.watchAcceleration(function(acceleration) {
        if(acceleration.x < -8) {
            shaking.left = true;
        }
        else if(acceleration.x > 8) {
            shaking.right = true;
        }

        if(shaking.left && shaking.right) {
            navigator.notification.vibrate(500);

            shaking.left = false;
            shaking.right = false;
            stopWatch();
        }
    }, null, options);

}

I just call it with

<a href="" onclick="startWatch();">start Accel</a>

But iOS doesn't react at all. Is there any special call you need to do in iOS?