I've seen a fair amount of discussion about connecting to a WiFi access point (AP) that has been set up to be hidden, but nothing much on setting up the RPi as the hidden AP. Being hidden, I don't want the WiFi name/SSID visible to mobile devices so that it can't be selected and you need to know the SSID and password to be able to connect. How can I set up Pi up as a hidden WiFi access point? (I have briefly looked at tutorials on setting up an AP, but haven't seen any on a setting up a hidden one).
Application wise, I plan to have an Android application that will know the SSID and password and can programatically connect to the RPi AP. What is important is the Android app knowing the connection state ("yes I am connected to SSID abc", i.e. the RPi), so I'm not worried about - and I don't think I want - is having the RPi connected to the internet. So, have the RPi allow Android device to connect, but don't do anything with web requests (I'm thinking it would be like "Connected, no internet access"). The reason for this is because after using the important 'connection state' the Android app will programatically disconnect from the RPi to allow the device to connect to the WiFi it had originally. (Basically the result of this, is that the Android app will kick off an action if the device is nearby the RPi, where 'nearby' is tested by connecting to the RPi as described).