The STD32 unit with 2 digital inputs and 2 digital outputs. Now supplied with water protected housing. If used with a fixed IP sim the STD32 can be configured and maintained remotely. A very simple application is to use it with an external relay to turn on or off central heating. This use can be further expanded by fitting a float switch to your Kerosene oil tank, which then sends a text message when it reaches a low level. If you call the device the call is answered, relay 1 energises, which for example turns on the central heating. As soon as the unit answers the call and the relay energises the call is dropped. Because the call is under a certain duration, cellular providers are not allowed to charge, which effectively means you have turned on you heating with no call charge. This is one simple application, the sky is the limit in terms of where the STD32 can be used or utilised.
http://www.gprsmodems.co.uk/acatalog/Telic_STD_32_and_35_Telemetry_Devices.html