A battery-powered device comprising: a memory storing software essential to the provision of normal functions of the device; a first processing section (16) comprising a data processor capable of executing the software, the device being capable of operating the first processing section in a normal mode in which it can execute the software and a low power mode; a second processing section (5) having a clock (6) for maintaining a time, and being capable of triggering behaviour of the device in response to the time of the clock preceding a user-set time by a pre-set advance interval; the device being configured to, in response to triggering by the second processing section when the first processing section is in the low power mode, cause the first processing section to enter the normal mode and to load the software.