For output on the PDA I used the LR 19kHz approach. I'm eager to see if an Android tablet can supply enough current for decent IR range.

For input, most cards can sample at twice the rate they playback (and some could do that on output). There were some that could sample at 96kHz in order to record CD quality which made it possible to get the IR carrier and determine its frequency up to ~48kHz.

It's still proprietary. I made the mistake of creating a freeware application that did not have all of its features and found RemoteCentral posts from users publishing all of the codes it had generated for them so I do not plan to release any source code any time soon.