Looks like they have sled brand specific units for a bit more as well, presumably to make install a bit cleaner. The $20 item claims to be not-for-apple-devices:
http://www.rsiracing.com/NON-APPLE-DUAL-USB-POWER-CABLES_p_102.html but doesn't say why, I'd guess that they found Apple equipment to be a bit fussier. They don't list that issue on the sled-specific models.
The kit is providing two standard female USB plugs to connect devices to. For $20, that's pretty decent, not tried them though and they don't list the wattage so not sure which units it will run.
Question I have, hoping you've used this with a Garmin GPS, is does it work? Many of the Garmins need about 1000mA to run and charge, lots of USB "power sources" don't put out that much power.
More importantly, those GPS units need a special cable to recognize they are getting power to run and not power to connect to a computer. If pin 4 on the mini USB cable isn't tied to ground, it will put the GPS into "computer mode" instead of "GPS mode".
I've used the Glisson and Garmin "direct wire" connection kits for the GPS units. GPSCity lists the Glisson for $22:
http://www.gpscity.com/gilsson-bare-wire-power-cable.html
Only trick with that setup is that the USB cable is on a 90 degree connector and it will not fit some of the Garmin models due to case or mount design. I've used the Glisson with my Nuvi 550 and (pretty sure) Oregon 450.
I normally run a Montana and 60csx, though I don't recommend 2 units for the average bear.