I bought a similar 'gadget' off eBay a while back - it cost about £5 or £6.
It was fairly cheaply made, as you'd expect - so I took the curved extension piece fixed a hose directly to it with a hose adapter on it. Then, using velcro straps I fix it to a harris pole. I've used it a few times for testing the gutters after I've cleaned them - to test the operation of the gutters, At least it will identify if there any leaks or blocked downpipes that may need attention.
To be fair - it's not up to much - but as it weighs about 5g - it's in the van somewhere.
For blocked downpipes I've got an attachment for the pressure washer extendable lance which can either send two jets horizontally along the guttering, or a single jet downwards. That would clear most blockages - and probably blow the end caps off too!!
Dave