At first glance this seems like it might be more complex than worrying about a computer. With a computer, a proxy like tor takes care of the ip and mac spoofing takes care of the rest. Android has more identification numbers such as serial numbers, ANDROID_ID's, ESN's and I'm assuming others. Does one need to worry about any other numbers besides IP and MAC being transmitted and potentially being used to identify them?
Furthermore, if one were to turn on airplane mode, activate orbot, ensure all data went directly through orbot, installed a softphone app, and coupled the softphone with some sort of virtual phone service, would this in theory allow for phone calls to be made without advertising identity and location to every cell tower in the area?