What replaces MobiTex for sporadic low bandwidth usage?
There are few options, which depend largely on your budget:
GSM, 3G, WiMax (If available in your specific country) and proprietary network solutions in the ISM bands (433MHz or 868/915MHz). A MobiTex node can be implemented with a modern sub 1GHz    transceiver, GMSK is available in many of those devices from Maxim, TI, Nordic and others.