To which bike and to which cradle is the device attached to?
On my 1600, the device in its BMW / Garmin cradle is fully enclosed within the dashboard. On firing-up the ignition, a fully flat Nav V will start, its power coming from the bike. I simply get a warning that the device's battery is low.
On my 1000XR, I think it does the same. I can check later as I have a fully flat Nav V to hand. On this bike, with its bog standard BMW / Garmin cradle (I haven't gone for all the 'security' cradle guff) I can reach around and operate the device's power on / power off button, very easily.
Both the above bikes' GPS devices' cradles are wired so that the power is turned on (and off) with the ignition.