Just a concept at this point, but I'd like to try out something like this as an RF transmitter / receiver:
Perhaps be able to make sub $20 sensor / transmitters that would send temperature information back to a base unit with the cell phone connection.
I am setting up a new farming area where I would have 8 to 10 mini tunnels. Some might be covered in plastic, some might not. It would be critical in the spring to know how hot it is in each of them.
I don't have much to add since my Arduino has not even arrived yet, but sounds like we are pushing it to the limit which is pretty exciting.
I'm going to get an uno and start fooling around with it. This is the project that has finally got me off my duff. Looking forward to working with y'all.