I'm working on a mobile device. Essentially it has nothing to do with WiFi communication. It doesn't transmit any data over the air.
It has to know however if it's in- or outside of the range of a given WiFi base station. (So basically it must be able to tell whether a WiFi network with a specified SSID is in the air or not, nothing more, nothing less.)
Do I need to put a WiFi module into the device, or are there any PCB components made specifically for this purpose?
(Power efficiency is a very important aspect as the device is pretty small and uses kinetic energy to charge its battery.)
Update: The device has an 8cc harvester that operates around 2 hours a day and is capable of outputting approx. 200 µW during a normal cycle. About once in every second month, the device connects a cellular network and does GPS positioning too. The whole process takes up 2-3 times 30 seconds on average. This results in a total power cons. of ~27mW/h. (If circumstances turn out to be fortunate it might be that this "energy-hungry" operation doesn't need to be done for a whole year or even for a longer period.) WiFi-monitoring described above must be continuous. (Manual charging can be a possible option if necessary, but it would be great to eliminate this circumstantiality.)