The Chrome Browser offers a programming environment, where independent application written in html and javascript can be launched. With a little bit of effort I was able to convert the app written for Andoid into a separate program working in Chrome. With some easy settings it was possible to enable communication with an external server (and a WAGO PLC is one) and to contact my controller's web server without limitation of the single-origin rule.
Here it is - an app in a beta state - made available in the Chrome Web Store (link). Obviously, you will need to have the Chrome browser installed on your computer, but besides it nothing more is needed. The app is very similar to the one made available on the Google Play (for android devices), and to the sub-page of this service (http://www.edom-plc.pl/wago/EdomApp/) published to make the configuration of the apps easier.
Please feel invited to use the app and to send comments. Your comments are the best source of new ideas.