Is it possible to reboot without stopping the engine?

Every now and again my satnav's maps don't load - there's just blackness - and various other parts of the system have had issues in the past, like the iPod track name freezing up. Turning the engine off and on again usually rectifies it, but that's not possible on the motorway as I discovered last night!

Is there a key press combination or something that power-cycles the system without having to switch off the engine?

I have similar freezing with my iPod connection. Would love to know if reboot on the go is possible too.