For cleaning windows from the inside, works for sash windows. You put one part on the outside and the inside bit holds on with magnets so you can move both parts up and down.
We did use it a few times to clean some windows we couldn't get to but then moved and it's been sitting in a box forever!
Magnetic window cleaner (Weybridge KT13)
This offer has been gifted to someone and is no longer available.