A good reason to go with the RasPi and a commodity USB Wi-Fi adapter here is that it will very likely end up cheaper than an Arduino (clone) plus a Wi-Fi shield

A good reason to go with the RasPi and a commodity USB Wi-Fi adapter here is that it will very likely end up cheaper than an Arduino (clone) plus a Wi-Fi shield. The latter can cost up to $90 [1]. Depending on where you live a TP-Link TL-MR3020/TL-WR703N wireless router might be a cheaper alternative to the Pi that has both Wi-FI and GPIO on-board but it is a bit more of a hassle to wire up. [1] https://www.sparkfun.com/products/11287 https://www.sparkfun.com/products/11287