using Arduino in a car

It has been discussed before but only in old threads which are now locked so thought I would ask again.
I am going to be using an Ardunio as the controller for various things on a custom car project (ok its a splitscreen camper!), TPMS tyre sensors, reverse parking, Airbag suspension pressure, etc…
There will also be other 12v devices powered in the vehicle, 19" LCD screen, LCD projector, etc… all of which are sensitive to anything but a stable 12v.

The voltage in the car will fluctuate a lot, when cranking it may drop to nothing, and when driving the alternator might push it up to 14.4v
All my electronics are running of a separate leisure circuit, but that is still that is driven hard by a Sterling 80A Alternator-battery rapid charger and a solar panel so range is 8v - 14.4v

I am thinking of using a step-up / stepup-down DC-DC regulator, something like this to supply 10A to the leisure circuit
http://www.ebay.co.uk/itm/DC-8-40V-To-DC-12V-10A-Step-up-down-Converter-UK-/321168603583?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item4ac723f9bf
I have a stet-up 12v-24v version to drive some LED bus lights and it works well.

or for more cash this looks good to drive 11A
http://store.mp3car.com/Carnetix_CNX_P2140_185W_DC_DC_Regulator_p/pwr-026.htm
and has the advantage of a second line giving to drive the Arduino 3A (would have to run it at 12v not 5v as Ardunio wants 6-12v)
It also has battery monitoring capabilities, V A temp; but with a PC USB interface, I wonder if it is just sending serial data and if we can interface directly to that with the Arduino?

Anyone have experience of issues i should look out for running an Arduino in a car?

Also I have not chosen my solar charger regulator yet so am wondering if any of the PWM or MPPT chargers have a regulator on the light/leisure output circuit, anyone installed one?