By now you might or might not have heard of OTOY, which in a nutshell, is server-side gaming. All you need is a computer, with an Internet connection. OTOY does all the heaving lifting with processing power; you worry about the gaming.
And lo and behold, the thing works on a mobile phone. Above, you see it in action on the Windows Mobile-based Samsung Omnia. Whether you actually want to play a first-person shooter on a 3- to 4-inch screen is a whole 'nother matter, but the premise definitely is cool. Check it out.