The minimum hardware will be Xbox level I guess.

The rendering will be done on their computer, not yours, so all you'll need is a similar broadband capability that you use for Netflix. This is basically an improved technology version of that Flight sim built into Google Earth but with Bing maps used as the base.

I don't think it's been announced how this game will be sold yet, but I suspect it will used as a carrot to lure people into a subscription service.