Based on the type, a tracking device can have or omit modules depending upon the usage requirement.
Broadly, trackers are broken down into 5 categories, namely;
Data Loggers: These devices log the position or the location coordinates of the device on the internal memory that can be later accessed through downloadable data.
Data Pushers: These devices are the most common type of vehicle trackers widely used. These devices usually transmit the data in the form of location, along with information about other on-board diagnostics to a designated server at regular intervals.
Data Pullers: Unlike data pushers, data pullers are always on and can transmit data as often as one wants to. Data pullers are more commonly used in conjugation with tracking devices with a GPS receiver module and a cellular network that can be triggered by sending a message wirelessly to it.
Convert Trackers: These are your regular trackers being put to use in everyday life. The only catch here is that these trackers are designed in a particular manner so that they mimic regular objects.
Vehicle OBD Trackers: OBD trackers can be easily plugged into the on-board diagnostics of a vehicle. The tracking unit is powered by the obd unit present on the vehicle. Additionally, OBD trackers communicate with other sub-systems of the on-board diagnostics to obtain data about vehicle performance, fuel consumption among other things.