Does anyone know how you go about making a system that could be activated remotely, like over the internet or phone. This would be like to trigger an input on the Arduino so it could go and do something. I know this can be done I just don't know what the parts are and how difficult/expensive it would actually be to pull off. Any ideas?
When you say 'activated', do you want it to be dormant in a battery saving mode up to the time of the trigger or will it be on mains power and active collecting data until it gets a request to transmit? How will you be returning the data from the Arduino at that time?
So, I'm thinking along the lines of building automation. They do this with lighting on really high end systems where I assume they have a PC running. The arduino system would be plugged in to an outlet, etc., and would get the equivalent of a button press from a phone call or something along those lines. Feedback wouldn't really be necessary, just someone calling the thing to tell it to start. Ideally, there's be an iphone app to activate the arduino system remotely... that sort of thing is what I'm dreaming of. Under $100 would be good too