In the past, I've typically used fuse taps when I need to add accessories to my car. This relies, of course, on the availability of unused fuses and the correct type of fuse (switched or non-switched).
Typically I run several extra compenents in my car; mostly not high-amperage items: Radar detector and an MP3 Player. I'm also a ham radio operator so I have my radio, but that is a high-amperage device, so it gets wired straight to the battery ;)
I imagine the new Rex isn't gonna have too many free fuse blocks, so I decided an auxiliary fuse box would be best; with some always-hot and some ignition-switched fuses available. I finally found the CirKit Boss kits which seem very nice.
I also mentioned that I run a radar detector; for the most part not because I speed, but because I like to be aware of what's going on. It's nice to know that there's a cop ahead and everybody will be slamming on their breaks soon - but you don't have to because you knew about it and are slowing down already. Newer ones can also alert you to emergency vehicles and are better at detecting the "Instant On" radar guns Cops have been using. Dennis and I decided to get the Cobra XRS-9700 because it's not insanely priced and has a good number of features and good sensitivity (or so reviews say). We'll see how it does coming back from Pittsburgh ;-).