A few days ago I bought a saw blade for pruning or trimming trees. It's from the Wolf Tools range, so you attach it to the handle of your choice, depending on how far away (read: high up) the branch is that you want to saw.
It has a curved blade, something I had taken for granted in tree-sawing blades before, but it has a subtlety of operation that I had not appreciated. When you use it with a long handle to saw high-up branches, when you pull it towards you the curve in the saw causes it to catch on the branch at the end of its travel. As a result it doesn't slide off the branch and start falling towards the ground, so you don't have to keep repositioning it.