The best gadget I have bought is a "ladder basemate" which allows you to adjust the angle of the ladder for uneven ground. There are two types one you put onto the ladder as you need it, the other which we use on all our ladders is fixed on, I think it costs about £40/£50. Been using them for the last four years or so and only replaced one yet.
Also love the aqua - dapter, ladder stand off, gutter vac, and so many other gadgets that you forget you have.
I would love an electric reel, and definitely the new pole ( or at least the connections) from Aqua- Dapter, also a drone for videoing some jobs. The wish list is endless when you start thinking about it.