Live tweet conditions from remote location

Hi all,

To begin with I'd like to say I have no prior experience with arduino hardware or coding. I have a little experience with RasPi's and a little bit of coding, although not enough for my intended project.

The idea of my project is to develop a stand alone device that will monitor certain conditions. It would need a power supply and internet connectivity so that it could tweet its readings at regular intervals, maybe every 6 hours or so.

As I foresee it, it will essentially be the weather station described here:

But with a GSM shield rather than an ethernet shield and a solar panel or a battery attached.

It would need to be waterproof and relatively small as to minimise the chance of being stolen or otherwise vandalised.

As far as I can tell this is in principle feasible, but my main concern is whether a solar panel will be suitable (particularly with regards to the size) or if a battery will be able to give it sufficient power for a prolonged period of time (a week minimum, but ideally a lot longer).

Does anyone have any experience or thoughts on how feasible this is?

Thanks in advance.