In telematics device mounted to a vehicle, an auxiliary processor detects an interrupt from an accelerometer and forwards the interrupt to a main processor—the interrupt wakes up the processor from a sleep mode. The main processor may then compare vehicle voltage and/or a value for a speed parameter to predetermined criteria to determine whether the interrupt was a false positive or if the accelerometer missed a detection of a user cranking up the vehicle. The main processor may also enter a conditional state if monitored information meets a minimum threshold. During the conditional state, the processor may operate according to rules for a current operational state and also according to rules for a changed state. The threshold for deeming a changed operational state is higher than for entering a conditional state to evaluate whether a change of operational state (i.e., on to off, or off to on) occurred.