Both the Cobb and the UpRev tuning are done by making changes to the factory ecu via the OBDII port (usually known as a ROM tune as you make changes to the factory ecu memory). Cobb has a device called the Access Port (which has been discontinued for the 370z) that allows you to change settings, UpRev has software that you would run on a laptop and connects using a usb cable.
Once the tuning is done no other hardware is needed, the changes are stored in your ECU. UpRev tuning is typically performed at a shop on a dyno (a list of tuners can be found here:
UpRev - Engine Management) although you can purchase the necessary software/hardware and tune the car yourself.