From what I've seen, you need to keep your smartphone turned on and with you. I'm fairly certain it's a "bluetooth low energy" connection between the smartphone and bracelet which technically has 160ft range but it sounds like the govt. is conservatively saying 30ft around a boat which would support the 160ft range. It's the smartphone that determines location; the bracelet is required to make sure you keep your smartphone within 30ft of your person.

You could move around your property as long as you carry your smartphone.