As the description says, you need to hack 30 machines at a distance with the Hack Tool. I'm pretty sure there isn't a specific distance, just that you need to use the Hack Tool to hack machines like cameras, health stations, vending machines, etc. Just use your remote hack darts to hack the machines and you will eventually get this in your playthrough. Sometimes when you hack a vending machine or ammo machine, it will dispense a hack dart or you can purchase one for $20 at those machines but usually they only have 1 for sale per machine.