....high fidelity....ah...no. I've never found any helmet mounted speakers that give great fidelity. I guess it really depends more on the helmet then the speakers. Obviously full face helmets are better then flip-up helmets in noise reduction but let's face it, riding at speed is a noisy proposition. I think any of those flat in the ear hole speakers aren't going to give very good sound at speed, and then there is the fact we should all be wearing some sort of ear plugs to protect our hearing.
With that said you might take a look at these products.
http://www.complyfoam.com/noise-redu...-mobile-phone/
I use them and they they work fairly well. They also offer decent hearing protection. You can rig the phone/mp3 ear phones so that it forms a pretty decent in-helmet system. I use mine with the my phone/mp3 player combo. I attached a little piece of velcro tap to keep the noise reducing microphone in front of my mouth and ran the wire around the side to keep it out of the way. My phone atomatically shifts to phone from mp3 when I get a call. While I don't recommend dialing phones or screwing with music lists while riding I do have Jot
http://jott.com/default.aspx speed dialed on my phone so that I can dial any of the numbers in my directory by hitting one button and use the Jott voice activated directory to make calls. Its a pretty good system.
...noise reduction
...mp3 music
...cell phone
cost under $70 bucks...oh...I guess you need to add a few cents for the velcro tape.
Hope that helps
added key words for future searches by forum members: Comply ear plugs noise reduction Jott phone MP3 cheap in helmet system music