Hi Tosh
Those things are not new at all. I had a customer that told me about them over 10 yrs ago, she had previously lived in a flat and had used them to clean her windows. The problem is the magnets dont always work and fall of the outside window which is good when you have it connected to a string. Only trouble is the string gets caught up as you clean. In the end you give up and get a w/c to do the job.
Steveyboy