Here's what I did for sound, I got:
http://www.amazon.com/Waterproof-Motorcycle-iPhone-Battery-Charger/dp/B005SE1ZQ6/ref=sr_1_1?ie=UTF8&qid=1330794672&sr=8-1https://www.denniskirk.com/408876.sku?utm_source=google&utm_medium=csehttp://www.amazon.com/ONEAL-TRACK-BLUETOOTH-MOTORCYCLE-HELMET/dp/B006ABIDA2http://www.calsci.com/motorcycleinfo/Concoursprod.htmlI thought long and hard about what case to get and I got the one I got because it is very weather proof and the screen can still be touched and work. it came from the U.K. but shipping was fast, took less than a week to get it.
The blutooth helmet is self explanatory but i got the calsci shield because the oem shield is so loud that you really have to turn up the volume to hear anything.
The install looks pretty clean, I run the power cord from the 12v outlet. I can use all functions off my Iphone 4s, including GPS. I usually listen to Pandora, but if someone calls,a simple tap to the blutooth on the side of the helmet lets me take the call. And yes, I can use Siri, just push that big button on the Iphone and speak away. Siri is gimmicky, but I find it most useful on a bike where you really need to keep hand action down to a minimum.
The way it is set up, there are a couple of ways I can remove things when away from bike:
1) Open up case, take phone
2) Loosen up plastic ball under case, take case with phone
3) Use techmount ket to remove it all.
I prefer #3 as someone might see the empty case and think "Hey, iphone!" rip the thing off then toss it when they find that there is no phone in it. I'll detach it and toss it into my trunk. The kit even has a rubber plug to cover the end of the iphone charge to keep water and dirt out- very nice.
Also, the case came with a nice lanyard, I have one end attached to the bike and the metal part to the iphone case to serve as a safety in case (unlikely) that something gets loose or break, sending the iphone off the bike.
It took me months of researching to come up with this combo for the perfect Iphone 4s setup.