Sorry for not responding. Data usage is responded here (just for reference for other readers).
But to clarify. At this point there is no possibility of extending the existing hardware with module that would allow for some gsm connectivity? I mean when you’re out there you need other connectivity types than Wi-Fi.
We are looking into this. Being totally strict, the only option to do so is to use the current auxiliary port and modify fhe firmware to send data to an external module via I2C (or other communication protocol really, as the auxiliary port is not strictly I2C, and can be mapped to other functions). This, however, would involve some knowledge of embedded programming and to understand the way the firmware works. Not wanting to discourage this route, but it would take some time and we are really very available for full support at the moment as we are busy with the following paragraph.
Since right now we are facing still issues with manufacturing, we are considering a hardware redesign. This new board, as @bryn.parrott suggests that would expose, as said above, some pins from the WiFi module (whichever we end up choosing) and, in that way, use it as a bridge to another communications module. This, however, would only be possible after we have new hardware ready.
Now, for this to be a standalone solution in itself, we still want to keep the wifi module in the board. The cost increase is not that high, but we don’t think it makes sense to remove it or make it swappable, but more to be a bridge to any other thing, that way, at least, you always have WiFi (remember that the kit is also used by people that are not so tech savvy as you are).