A periodic "ping" from a GSM module attached to truck, car or shipping container is commonly used to provide location information back to a control centre. The same technology is equally applied to tracking individuals whether they be lone workers or those working sensitive areas where the use of panic alarms is necessary in case of emergency. Determining the location of something through mobile (or wide area) networks is one of many uses of M2M (machine-to-machine).
The use of SMS in these situations is often to compliment GPRS data but you might ask why use SMS at all when GPRS should suffice? The answer is simply that GPRS is not always available, particularly on 3G networks but also on 2G networks, in the location in which the GSM module is located. It's a fact that it is more likely that SMS will continue to be available where GPRS is not possible due to, for example, distance from a base station, interference or being located within a building.
M2M is a growing area with its roots in mobile telemetry and is a subset of the "internet of things" in which millions (more likely, billions) of mostly simple machines will communicate with each other and centralised systems. GPRS will play an increasing role in M2M as the number of M2M devices significantly increases. SMS will also play an increasing role in M2M, again as the number of devices increases, but also as it will continue to be a service that is available where GPRS data is not.
