The Committee has in the past insisted on only using Privateer Press model cards or War Room to track damage to minimise any chance of misunderstandings.
Times have changed however. A number of Theme Force lists have risen in popularity which require tracking the damage on many different jacks/beasts. In addition, many accessory companies have created high quality tracking devices for use in the game.
Therefore in recognition of the changing times, the Committee will allow alternative damage tracking methods at the WTC this year. You must ask your opponent if they are OK for you to use them and also understand how you will use them. (We recommend you have cards or War Room handy as a backup as a result.)
Keep in mind that it is entirely up to the player to do this properly. If any tracking method is found to be faulty (deliberately or not), the repercussion could be as high as expulsion from the event.