How about the cigarette lighter in the console? It's easy to get to and as an accessory, it requires a good deal of current to heat that up, so you know that it's well fused.
I in-lined my radar unit in my (former) Mazda MX-6 using the hot lead off the sunroof control...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car