Sema SMH10 works great and can connect to a MP3 with a plug plus 2 bluetooth devices. This system mounts to your helmet and you can either use speakers (if your helmet has earpads) or earbuds.
The downsides of any system are going to be range and windnoise. I suggest checking out www.webbikeworld.com
and reading reviews. This website tests almost everything motorcycle and is a great tool if you like unbiased reviews of products you are considering purchasing.
Please note that I am in no way affiliated with Sema or Webbikeworld; I own the a SMH-10 (dual pack) and have used the website to research most of my gear.
Also note that once you find a system you like check ebay before you buy in a store. I saved about $75 using ebay compared to store price.
Retired USAF, IYAAYAS!
2008 V-Star 1100 Custom Bobber project
2011 Crimson XR with Forged Highway Bars / Hard Bags / Passenger Backrest, Ness parts including Smooth Layback Plate Frame/Mount / Rad 3 Mirror / deep cut grips / drivers floorboards /shifter peg / brake peg / passenger pegs. Witchdoctor black rack, Lloydz filter / timing wheel / VFC III, 7Jurock windshield, Drag Specialties seat.