I am looking for cheap way to have very basic wireless communication between an Arduino and a iphone. I don't need to send complex data, it would be sufficient to "trigger" the arduino: let's say it is reading a certain pin voltage and waiting for it to be up in order to do stuff, my goal is to trigger this pin up by any (wireless and iphone friendly) mean.
I have figured out two solutions: wi-fi shield, cheap RF transceiver. The problem with the latter is that it is not trivial to communicate with a RF transceiver from an iphone. I should add another arduino controlling an RF transceiver on the iphone side and commanding this arduino with an usb.
The wi-fi shield on the other hand is too expensive. Even small routers such as the wr703n (30 euro more or less) is too expensive in my opinion. I just want to send a "bit" of information, so I don't want to spend more than 10 euro.
The third option would be to hack some cheap wi-fi controlled tool, such a lamp or plug: do you know any? Do you have any other idea?