griffen tech sells a program called total remote that lets you use your pda as a infrared remote. for pdas without an ir port, it also comes with an audio-to-ir adapter that plugs into the headphone jack.
scotty-o’s pocket pc phone had an ir adapter, but he wanted less pathetic range and he didn’t want a silly ir adapter hanging out the side of his phone. so he did what any self-respecting hacker would do: he took his phone apart, hard-wired the adapter circuitry to the phone’s audio output, and reassembled it all back into the original phone casing. nice!