You wear a small machine called the "Tropper" that catches the rope tightly while your hands are free. Each tree has a Jumping Pad marked on it, and a rope leades to each pad. In order to climb up or down the rope use the Tropper. (It has a ratchet like action, and possibly a small extra motor to assist
Ropes are brightly colored, to stand out, so that you see where you next rope is.
Each rope has GPS RFID locator, so that you know next rope is available. When you hold the rope, the next rope is alerted, your rope gives the ok sign (beep, and LED), and you jump. If someone needs your rope, it is giving a sound and blinking in a way, that you know you must wait before steping onto the tree high jumping pad.
Start this as a "theme park" game. Would make theme parks have more real trees. Or start it in a public park, with city permission. Of course you would have to have safety nets where the hoppers reach high above the ground.
Once successful, this sort of transportation could become the main 21'st century city mass transit technology.