Anyone used these? Seem like a great way to know when to transfer to secondary, or when primary is complete, without having to waste beer by taking a hydrometer sample.
http://www.austinhomebrew.com/product_info.php?cPath=178_67_64&products_id=12581
http://www.austinhomebrew.com/product_info.php?cPath=178_67_64&products_id=12581