sitzikbs, I'm working on exactly the same project!
I had a lilypad lying around, so I did my prototyping on that before I went and ordered a Mega compatible microcontroller off eBay.
I found this IR library, which is excellent: http://www.arcfn.com/2009/08/multi-protocol-infrared-remote-library.html
and after much probing, discovered that AC remotes send out the entire state of the AC, and thus the signal they send can be quite long. This modified version of the library takes care of that: 64-bit RC6 codes, Arduino, and Xbox remotes
You could use this library to record the codes your AC remote sends, and then repeat them. I found that creating a simple oscilloscope via an LED plugged into the mic in and running Audacity is a good way to double check the codes interpreted by the above library. If you want to take it a step further (as I have), you could take the time to reverse engineer the IR codes your remote uses, and expand on the library (or even contribute the codes to LIRC).
The next step is creating a webserver on the arduino, and having it serve a simple page to the phone's browser. The treeduino looks useful. I'm going to go over that myself too.
-Ethan