Spark core is a low power ARM Cortex M3-based board with WiFi onboard. Very neat.
I can give you several good reasons why it is more useful to do this with a Spark core (or an Arduino), but the most important to me is that learning how to program very constrained hardware platforms is useful.
A similar product that has been around for a little longer is electricimp (http://www.electricimp.com). I've done a couple of little projects with it at home, but is has also been used in several consumer products already.
I can give you several good reasons why it is more useful to do this with a Spark core (or an Arduino), but the most important to me is that learning how to program very constrained hardware platforms is useful.