I don't think you can create such an application without some technical knowledge.
You can create those drawings in Inkscape for each house automation case you need. You already have the parts created in one page, so you can use that page as a library of symbols. When creating a new house automation plan you just copy all the necessary objects from the library into that file. You can turn on Grid so you can easily create the wires that connect various objects in your drawing.
But if you need an application that will do something more than just create a drawing, for example if you need to create a simulation of the device you'll need someone to build it for you. If you only need a way to make the wires "follow" the objects as you move them you can use Connector tool in Inkscape, and for some more advanced behavior try to find a Javascript based SVG editor, maybe this one
http://code.google.com/p/svg-edit/