I've actually got a iPAQ H3630 as well. There was a big effort a while ago on the Linux mailing list to find a way of attaching a standard USB keyboard and mouse which are both slave devices to the iPAQ but from what I remember there wasn't any workable solutions.

You may want to get a CF sleeve as it's quite a bit cheaper than the PCCard sleeve which has to include an extra battery.
Another method would be to connect to the Empeg by IrDA but you'd need to keep the iPAQ pointing at the Empeg display.

- Trevor