Fetch value from a URL. Make sure to enter a correct URL, e.g. http://www.yoursite.com/get_value.php
The plugin will try to retrieve the content of the URL and parse the body. The response will be taken as the element’s value.
The Bitcoin Calculator Example takes uses this option to retrieve the current BTC/USD price. The response is a JSON object so you will have to specify which key should be read in the Value_http_json option.