A fuse is not a switch, it does not turn a device on or off, it only protects it against over-current (too many amps). If it is wired to a circuit that is hot all the time (unswitched), or to the battery directly (with an additional fuse at the battery to protect the wire), it will be on all the time. If it is wired to a circuit that comes on with the ignition, like the switched accessory circuit, it will only be on with the ignition. Yours is likely protected, at least at the GPS, but it wouldn't hurt to check, or ask your tech how it was wired, and to what.