Is there a bitcoin robot? Is there a bitcoin robot that can automatically trade bitcoin for USD?

I see that bitcoin rates fluctuate every day and has different rates at different exchanges, and it could be easily traded like other currencies.

So, is there a bitcoin robot, similar like forex robots?
I tried writing one in 2011-12.  I ended up doing a lot of volume, but I only broke even because of the commission.  I generated a lot of money for Mt. Gox though!

In general, writing an automated trading program is always going to be a difficult task, because anyone who can write a superior program can cut into the profits of the inferior program, which leads to a development arms race.  This is what some hedge funds do (not with Bitcoins), but any models they develop are only expected to make money for a short amount of time.

Even if someone released a high-quality open-source program, it would be difficult to make money by using it because so many people would run it.