The new Arduino 1.6.x IDE makes it fairly simple to use the ESP8266 modules. I have been meaning to play around with a some open window detectors for a while now. I notice two dedicated GPIO pins on the ESP8266, which is one more than I really need. So I threw in an led which turns on when the window is open. Nothing like local, direct feedback that the device has detected the state of affairs. The reed switch is attached on an interrupt so as soon as the magnet gets too far away the light shines.
I will probably fold and make the interrupt set a flag so that the main loop can perform an http GET to tell the server as soon as it knows when a state has changed.
Probably the main annoying thing I've still got is that during boot it seems the state of both the gpio pins matters. So if the reed switch is closed when you first spply power then the esp goes into some stall state.
It will be interesting to see how easy OTA firmware updates are for the device.