In the past, I've used my Pocket PC handheld as a universal remote. One hitch I've came across is that it had a very small range. I'm sure you'll do this but just make sure your IR transmitter has enough power to transmit to your robot across the field. The range on portable devices with IRs (palm, pda, psp, etc) is considerably lower than the range on a standard remote. Besides 'style' I see no reason to use a PSP in place of a standard universal remote that will probably get a longer range anyway. That's what they are made to do anyway right.
There's no rule against it, though, so go for it.
