1. A method for providing theft protection for a portable device by a theft protection sub-system, comprising: operating the theft protection sub-system independently of a processor controlling the portable device; by the theft detection sub-system independent of the processor, detecting an acceleration of the portable device; generating an acceleration signal in response to the detecting, the acceleration signal having a spectrum of frequencies characteristic of accelerated movement of the portable device; processing the acceleration signal by analyzing at least one metric indicative of a degree to which the acceleration signal matches a known theft condition; generating a theft detection signal only when the analysis of the metric indicates that the degree to which the acceleration signal matches the known theft condition is greater than a pre-determined threshold value; sending the theft detection signal to the processor in order for the processor to initiate the production of an alarm based upon the theft detection signal; and disabling operations of the portable device other than the theft detection sub-system and alarm by the processor, wherein the processor is arranged to enter a sleep mode to conserve electrical power consumption by the portable device and the theft protection system is operable when the processor is in the sleep mode.