I don't think the real challenge would be the design and construction of the IR hardware, as you point out. The components are fairly cheap and the design itself is hardly a challenge. The real issue would be writing the app that would be needed to control the IR device.
If you feel like learning how to develop your own apps you can do so for free. Go to iTunes on your iPad, click on 'iTunesU' at the bottom right hand side, select 'Universities and Colleges', then scroll to Stanford. Scroll right through the courses and you'll find a two-part, 25 lectures per part, course on programming iPad apps. It's free and, by the end of the course, you'll be able to program some simple apps yourself. It's a great resource from one of the best Universities in the world.
As you'll be able to see, app development is a fairly involved process requiring a significant background in programming as well as access to a Mac computer, the iPad SDK and registration with the Apple Developer's program.
Tim