The problem with gsm is that it eats batteries. For many "internet of things" applications , a long range , low speed, low power network might be a better match.
well, my point was to have several devices utilizing bluetoooth(or any other low power/short range comms) to talk to a central unit, that could be plugged in, that then conveys info via gsm. the more I think about it though, the more it would make sense to just have your central "hub" hooked into a router instead...