While this is a decent idea in Theory, it's not very practical. My PC is on the second floor of my house, and my entertainment center is down on the first floor.
Buying this app would cost a LOT more than just the very high app price, since I would need to run a USB extension cable about 100 feet and then buy the iR transmitter as well.
Like I said, good idea in theory, but NOT practical. ( unless you can make the screen flash a powerful iR pulse at whatever device you are trying to control, and we know that's not possible)
I tried something along these lines years back with my Treo. Novii Remote was not a very good app the usability was poor at best. On a related note, I jumped back into the world of unified remotes with the Harmony One which was on sale at Dell. It's pricey, but man it works great and doesn't leave me wishing I was using the TiVo peanut (which I still believe to be the best remote on the market). The Harmony 550 is also well reviewed, but without the bells and whistles.
I have a Harmony 895, which is a great remote. However, the beauty of the Intelliremote app for iPhone is that it supports AutoIt scripting so there's no limit to what you can do with it. I also have it operating X10 devices to control lights, garage door etc, all from my iPhone!