Sorry, spark.io is down and I'm not sure what it is: A dev-board? Why not use an RPi instead of an arduino for something like this? costs ~ 25-35 USD (depends on model) + a WiFi dongle and you can write code in Ruby/Python?!
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.
