Checking Contents of Shopping Cart using Liquid

BC allows the cart to change without an associated page load, so if you could get the cart data through Liquid it may not always be accurate.

A little Ajax would do the trick. Just retrieve the same page via Ajax, and inspect the contents for the cart.

You need none of this.

If you do the code within the specified template for the cart that already exists, even with liquid - BC has the stuff in place and it will update.

If you are doing the cart information through a collection, outside of this scope, all you need to do, say with jQuery is the simple .load and partial refresh a page (google, easy to find) and you would need to hook into that on times say add to cart is fired.