SMS spy tool is the applications that are programmed and is designed for controlling and monitoring any device.
It is actually a virtual device that one has to install over the targeted person device to figure out everything in hidden mode.
If you are making use of Smartphone then obviously you might be aware of those.
Similar to other apps this tool is developed by the application developers.
This can track the messages, history of call logs, contacts, location etc.Spy tool is fully capable of doing many activities.
A person can use the spy tool but there are a few things that one has to consider and for knowing what software can actually do.