I'm making a similar project, but without the wireless part. I really wanted wireless but the climate here just won't allow it. It can stay below freezing for months in the winter and I know even with a SLA battery I'd have power issues in that kind of prolonged cold. Plus, the sun can disappear for weeks here. Therefore I ended up running 100ft of cat5 to my outdoor sensor station, and dropping the clock rate for the sensor communication, given capacitance issues and such caused by the long cable.
I'd also be careful about program memory. Mine disappeared fast when adding an ethernet shield and code to communicate with the multiple sensors, and I had to upgrade to a mega, which I am waiting to arrive before continuing my project. You might want to just get one of those instead of the uno and save the trouble of running out of space.