Find My iPhone Without Registered WiFi
What alternatives to Find My iPhone exist that do not rely on the iPhone physically being connected to a "Registered WiFi?"
My iPhone is almost always connected to the Internet via a cellular data connection, comparatively rarely connected via a Registered WiFi. It also always has GPS turned on.
Same holds true for my wife. Indeed, it is rare that we can find each other using the Find My iPhone app running on each of our iPhone 5s, simply because one or the other iPhone is not connected to WiFi, but instead is connected to the Internet by way of LTE or 3G. We can rely on texting or simply calling, except when either of us happens to be driving (phone use while driving is ellegal here).
We both increasingly opt to dismiss WiFi connection prompts place-by-place simply because connecting to the Internet via LTE or 3G tends to be a more reliable, faster connection, not to mention more secure. Most heavy Internet usage is done either at home or at work where we each have good, reliable, secure WiFi, and thereby don't unnecessarily run up data usage charges.
Ideally, there must be some app out there that works by way of the "lost" iPhone having any active Internet connection, not just via WiFi.
I've searched the app store and Google, to no avail. I've also searched these discussions and have found some others seemingly looking for something similar, but no definitive, workable answer. So, thanks for your knowledgeable suggestions.
iPhone 5, iOS 6.0.2
