OMAP5 looks like the obvious choice. But a SoC with more powerful GPU like the 'Rogue' series would be very nice, like ST-Ericsson's A9600. I'm guessing it could handle PCSX2 if it gets ported ARM architecture.
It's probably for Michael Abrash's wearable computer project:
http://blogs.valvesoftware.com/abrash/valve-how-i-got-here-what-its-like-and-what-im-doing-2/