Communication from Arduino to Android App

Hi, can someone give me the steps on how I can get the Arduino to send a simple message to my phone or app? I need it to tell me when the light changes in the environment and then shut off when it changes again. I want the message to be sent wirelessly over the internet so the arduino must be capable of sending the message wirelessly. What do I need to buy? Any diagrams or videos I can watch to make this happen? Thanks.

civilrights_83:
how I can get the Arduino to send a simple message to my phone or app? I want the message to be sent wirelessly over the internet so the arduino must be capable of sending the message wirelessly. What do I need to buy?

It this juncture, the only answer can be "lots of stuff, most of which you won't need". The first thing you would be better off doing is some more research on what you actually want. Understanding the difference between a phone and an app would be a good place to start. Arduino can send messages direct to your phone. This could be the simplest, cheapest, and probably the most appropriate way of getting a short message out - no internet required.