it is in many a very key functionality of home automation. There are a whole bunch of things you what to happen… only if someone is home.
There is in fact a general agreement in this community as to which strategy is the most effective. In fact, Rossko mentioned it a few replies up
Using several methods, and then combining the results and making an educated guess at the accuracy of the individual components. example
Think about what you really need to know (am I close enough to home to fire up the heat?) Well… where did you leave from? What if the notification can be sent when you leave a region (heading home from work?)
Not saying this will work for you, just trying to give you some ideas about how to think about the problem and invite ideas about how you can provide a working solution.
You are after all trying to predict something that is yet to happen in the future. (I’m almost home, fire up the heat) Not to be a smart a$$ but what if you get in a wreck a block from home? Heater fires up, malfunctions and burns house down while you are being brought to the hospital… 
… kidding but you get the point