NEW PROJECT tweetable wifi mist/fog machine - feasibility and advice please

Hello, I plan to create a mist machine that can be tweeted to activate it.

The unit will not have mains water supply, I will use a unit with a storage tank -

I will not be able to fit an ethernet cable, I plan to use the wiFly shield with an arduino Uno. Tweeting the unit will activate the pump.

A couple questions..

Will the wiFly shield work with the twitter library? What is the best way to get an instant result from the fogger? Will a transistor work when trying to control the power to the fogger from the arduino?