Your concept will probably not work because the audio output on a phone only goes up to 10 or 12 KHz, maybe 20 KHz at the most. Frequencies for remote signals are typically around 430 MHz.
You may find some interesting information about the Redeye Mini on www.redeye.com
. What is actually in their little dongle is surprising.
There is a lot of information on this site about remote codes and how they are structured. They are not all done the same way. There are some utility programs available for creating/decoding the ir commands.