Acknowledging the limitations of a house interview, Intel's piece on Roy Want and the personal server is interesting. For what it leaves out.
Slap Bluetooth on an iPod and don't you have a personal server? Want's a smart guy, and there's smart folks in the group, but what's in the article doesn't sound particularly challenging.
Also, I'm wondering if users will really bite on a device that is always dependent on other components. Strikes me you'll have to attach some kind of I/O just so the server isn't rendered completely useless in places where it's inconvenient to install the supporting technology. Maybe the deal is to make the server fit in your shoe (a non starter unless you expect to wear the same shoes every day), make the cell phone the minimal I/O device, and then if you get in presentation rich spaces interact.
Okay now there are issues.
And making the server into jewelry (ring, bracelet, belt buckle) might be a better bet.