OK. Terminology clean-up.
Powerlet indicates using an auxiliary plug, usually "BMW" size.
Your stated accessories probably would be better "hard wired" than plugged into 4 outlets... poking out from various locations on your bike.
To give you an alternative view, here's an example of how I've installed: Valentine One; Garmin GPS; Autocom sound system; Gerbing heated clothing
The battery is located forward, right side. I run a 12ga, independently fused pair, behind the B&D panels to a BMW outlet (from BMW) located in the B or left, upper panel. This allows a Battery Tender to be used if the bike must sit for some weeks. I wired up a BMW male plug to my Garmin's "hard wire set-up" and plug it in here when I want to recharge it, or run its back light -- but really, it's plugged in every time I use it. This separate,30A circuit, will also easily power an air compressor -- if needed.
I ran a second independendly fused pair (30A). Negative (Ground) is to a "barrier strip", or Connector Block. It provids an easily accessible source of Ground for any forward mounted accessory. Positive is also routed to a (second) "barrier strip" or Connecter Block through the high current side of a relay; Activation of the relay is via one of the windshield "input" lines. Hence I have a block of eigth swiched "outlets". The V1 is wired to one of those... and to ground. This would be a sound power source for your iPod (whatever that is), your heated grips, and even your heated clothing (with a reservation).
I chose to run power aft from the battery, across the engine bay and beside the tank through a NAPA glass and silicon spark plug shield to protect the wire from excessive heat. That sheild also protects the Ground Loop Isolator carring the audio signals aft from my V1. I don't use the audio available from my GPS, but if I did, it would be routed through here, as I suggest your iPod output be done.
The power for my Gerbings has its own fused line, and can run from either my forward connector block or battery. It "pops up" between my seat and the rear of the tank. I connect my controller with a two prong, SAE plug.
The Autocom resides in the tail cone. Power and ground come from tapping one side's tail light lines. The audio lines run back to it, with passenger output able to be exposed between the seat and body work, and rider output between seat front and tank.
This seemed to be the minimum of "running wires fore and aft" -- in this case, "wires" only run aft.
If you are thinking of actually hearing the iPod, I'm going to guess it's a music player with very low power output - some "extra" solution will likely be required. Whether "pluged into the bike" or run from its internal batteries, the lines would run above the tank, perhaps into portion of a tank bag where you had an additional amplifier, like a Boostaroo. Speaker lines then would run from tankbag to helmet - and whatever speakers you decide upon.
Second way is to run the iPod output (under the tank) to a distinct, "universal" amplifier, like an Autocom. Then take sound output to helmet speakers or in-ear speakers from the Autocom. If you do this, powering the Autocom with "Bike Power", and also power the iPod with "Bike Power", the circuit created will act as an antenna and definitely will pick up ignition noise. Hence, running a Ground Loop Isolator from any sound output device to the Autocom.
All this is complex, and I'm certain my descriptions are not the clearest. But "Your Professional Installer" should be able to explain it BACK TO YOU. If he/she cannot, go find a REALLY competent Installer who can.
There are many options of wiring that will provide for some, most, or all of your current and future needs. I hope I've opened up some of them to view for you and your Installer.
Best wishes.
