It spooks me every time it happens. I know what is happening, but the ghostly voice still sends a shiver down my back. I refer, of course, to my TomTom satnav device. Nowadays I'm mostly to be found in the centre of a city and usually use public transport to get around. So, I don't often have to often use the satnav device for my car. However, if I go somewhere unusual I'll take the satnav unit into the car, plug it into the power and let it quietly tune into the satellites as it recharges its batteries. Sometimes I use it to check the route if I'm uncertain. Once home I'll switch it off and chuck it on a shelf for a few weeks until the next trip requiring navigational assistance.
It seems that pressing the off button does not totally power down the satnav unit. It will continue to operate in an almost quiescent mode, but showing no signs of life. As the internal batteries drain they gradually get close to a level of electrical exhaustion. For some reason at that point the satnav unit autonomously switches itself back on and attempts to navigate the last chosen route. Suddenly while I'm quietly working in my study, a ghostly voice will drift down from the shelves above my desk advising me to: "Turn left at the end of the road".
This suggests a plot for a future book... people being monitored in their own homes by devices they thought they'd switched off.