Well, I dont know if this one would be classed as an "essential" tool but thoought I would put it out there as we are now have more electronic gadgets than tools.... (What ever happened to a map, compass, pencil and paper... the good ole' days?)
You can now get an App for your iPhone from Nissan with some tools including a trip planner and logbook ledger. You can also call Nissans Road side assist. Just to name a few.
They even have a "Parking meter timer" which will alert you (after you set it) to when the meter needs to be fed.
Here is a link to the website...
http://www.nissan.com.au/webpages/ow...iPhoneApp.html
Cheers,
Rob