One option, custom audio earplugs. Block out everything and keep the volume down. Has wires. http://www.westoneaudio.com
I used to use in-helmet speakers (tork x-pro) with custom molded musician earplugs with adjustable db filters.
I needed a boostaroo with an iPod:
I still use the custom earplugs, but just connect via Bluetooth to my iPod now with a cardo G9 wireless helmet system. Proper speaker placement is key, but it is loud enough.
Another item that is very important...a quiet helmet. Keeping the wind noise down keeps the music volume down.