1. Some of my HJC helmets (like the Symax series) came with removable "ear pads" so products like the Chatterbox speakers could be inserted. These pads were conveniently held in place with velcro.
My homegrown solution:
Disassemble a set of headphones. You want the speaker and the wires only.
Cut a slit into the pads.
The speakers will fit into the pads. At this point, you must use caution as the wires at the speaker are soldered on and easily broken.
Most headphone sets will have some sort of tension relief (kindof like a knot) that will reduce/prevent strain on the wires leading to the speaker. If you have this, place the tension relief inside the pad and sew the pad around it. It doesn't have to be pretty...
If you don't have a tension relief, you can create one by using some hot glue on the spot where you want to have the relief.
2. I ran the cord under my jacket to a waterproof clip-on stereo on my belt that I picked up from Radio Shack for about $20. That worked a lot better than the Scala Rider even though I can't answer my phone that way. As it turns out, I can live without the phone while riding. What an amazing concept!
Cost: ~$100 - $150
3. I've also used the inexpensive Sony "over the ear" headphones for shorter rides (less than 40 minutes). They are somewhat uncomfortable for extended periods of time, though you get better sound quality than any kind of speaker not "inside" your ear. These headphones also help block out road/wind noise.
4. The most expensive yet effective option I've to-date heard about involves going to the hearing doctor who can take a mold of your ear and have something like the Koss speakers imbedded in them. I've ridden with just ear buds and never been comfortable with them, nor have I had great success getting them to stay put. This sounds like the ultimate option, but I've never laid eyes on this setup. I'm not sure if the guy telling me this was full of himself or not...
Cost: $200 to $300
5. Whether you ultimately decide to destroy your hearing from music or road/wind noise is up to you. After my wife started complaining that I kept turning the TV up too loud, I started using disposable ear plugs (which are the cheapest and most effective) to prevent additional hearing loss. Don't need music when the machine makes its own