What about my phone?
Your PitPat GPS Tracker does not talk directly to your phone. Instead, it talks via our internet "cloud" service. That means that theoretically you can be anywhere in the world and still track your pet anywhere else in the world (as long as you and they are both in coverage).
Any internet connection will do. When you're out and about, that'll be via your mobile data plan (any network is fine). If you're at home (or in certain other places), it can be a WiFi connection to the internet.
The PitPat app uses very little data compared to other things, so you don't need to worry too much about exceeding your data plan.