What about the people who don't have phones or have flip phones? What if your phone is off? And I'm assuming GPS needs to be on for this as well.

Though if Australians had balls I could see having a lot of fun with this. Just not do it everytime even if you're home so the cops have to respond and be like "oh, left my in the other room," "was on a call when you texted me," "sorry was having a nap." See how many times the cops will actually show up.