PHP: I use the file file_get_contents to receive information from chaturbate.com/user and then I make a preg_match to see if the text 'currently offline' is found.
JS/AJAX : If the text 'currently offline' is not here I'll get a notification sound on my computer.
It's is pretty easy and I made the script in a couple of hours. I could send it to you if you'd like.
I've been studying Android Studio and it seems easy-going, but I would still need some help making the convert.