People like to spread the rumor that gateway bricked random consoles, but in reality it did not. These people are uninformed and like to jump to conclusions. It only bricked consoles who used a clone card, NEVER an actual gateway card user was bricked simply by using it how it's intended.
Making brickware for the 3DS is relatively easy from what I heard, but luckily no one with enough knowlede of how to make it has ever tried afaik.
EDIT: Just saw the person above me thinking exactly how I said. The reason Gateway is not brickware is because everyone is fully aware it did contain code to brick consoles and everyone knew exactly how and how not to trigger it. If you know exactly the cause for the bricks and the solution, it really isn't brickware. Plus that's not it's sole intended purpose