So then the answer is what Ulf said first: the device needs an ip address or name the android phone can use to find the device. It will also need to have some protocol for communicating - for example a small OS that runs a web service or the like.
One protocol I have used for this sort of thing is MQTT (
MQTT.org). It is a simple protocol used in 'the internet of things' that lets devices (like your air conditioner) send and receive information based on topics. You have an MQTT broker installed on a computer, have the air conditioner and the phone connect to the broker then have fixed topics where the air conditioner publishes its settings and current temp. Then a different set of topics the air conditioner listens to for changing those settings. The phone subscribes to the current settings and the temperature and can give the user the ability to change the settings using the second set of topics. It is flexible, and gives you room to add multiple air conditioners or other appliances without having to connect to multiple servers/ip addresses. For the broker Mosquitto (
mosquitto.org) works well and for Android the Java-based Paho client code works well (
eclipse.org/paho/).
But that is just one way. There are many options to choose from and what you choose to do on the hardware will narrow your options for the android device.