These modules have Wifi (duh), UART, GPIO and are programmable in Lua.
Just think about it - a Door sensor for the price of this module (< EUR 10), a reed switch with magnet and some power... yes, it's possible! (haven't tried it yet though, but I'm going to

If you like what you've read so far and want to know more, you should also read my recent post about those modules - it can save you some time getting things going

http://blog.hekkers.net/2015/01/01/meet ... ansceiver/