My 2015 had a TomTom rider wired in by the dealer as it comes free with the bike at the moment in the UK.
I have not traced through the wiring myself but the dealer told me it was wired direct to the battery so it could be used whilst the ignition is off and also that it is fused with the fuse being located under the seat near the battery.
I don't see it being wired directly to the battery as a problem as I would not risk leaving the device plugged into it unattended.
I think a relay is more important with things left on the bike when it is not being used like heated grips if they don't switch off automatically like the newer Oxford ones claim to do.
I hope this helps,
Gary
