Easy? Sure. Here’s the method:
Reliable? Presence, no matter what method you use, is one of those things that vary greatly from household to household because of many different factors. Where you live (cell tower location, local topography like hills), how you use your phone (including how often you turn it off), local radio interference: lots of factors affect performance. So two people can have exactly the same phone model, configured exactly the same way, and presence will work great for one and be frustratingly unreliable for the other. You just have to try one method, see how it works, and if it doesn’t work well come back to the forum and people will help you troubleshoot that method or suggest another method to try.
If you do have to come back, please list the specific model of your phone and the country you are in, that can make a difference in the options available.